AU2019431265A1

AU2019431265A1 - Residue processing method and sulfatizing roasting method

Info

Publication number: AU2019431265A1
Application number: AU2019431265A
Authority: AU
Inventors: Kenzo Sauda
Original assignee: JGC Corp
Current assignee: JGC Corp
Priority date: 2019-02-26
Filing date: 2019-02-26
Publication date: 2021-04-08
Also published as: WO2020174573A1; JPWO2020174573A1; PH12021550518A1

Abstract

This residue processing method is characterized by the application of a centrifugal force on a residue containing a nickel fraction and iron oxide to separate the nickel fraction from the iron oxide.

Description

DESCRIPTION RESIDUE PROCESSING METHOD AND SULFATIZING ROASTING METHOD

Technical Field

[0001] The present invention relates to a residue processing method and a sulfatizing roasting

method.

Background Art

[0002] In the related art, a nickel sulfate compound is used as a raw material of various nickel

compounds or metal nickel for use in, for example, electrolysis nickel plating, electroless nickel

plating, and catalyst materials. The recent demand for secondary batteries using a nickel

compound or metal nickel in a positive electrode material is expected to expand as a power supply

of transport machines, such as electric vehicles, and electronic devices. To produce high

performance secondary batteries, there is a need to stably supply a high-purity nickel sulfate

compound.

[0003] Examples of impurities that may be contained in low-purity nickel compounds include

other metal compounds, such as iron, copper, cobalt, manganese, and magnesium compounds. In

the related art, examples of a method of obtaining a high-purity nickel compound include a method

of dissolving metal nickel having an increased nickel purity by an electrowinning method in a

sulfuric acid solution and a solvent extraction method. The solvent extraction method involves

a process of removing other metal compounds by selective extraction or taking a nickel compound

out by selective extraction. In both cases, a particular agent is needed to selectively extract

particular metal ions, resulting in high costs.

[0004] Known methods for manufacturing nickel sulfate also include a method in which the

anion of a nickel compound is exchanged with a sulfate radical by ion exchange, and a method in

which a nickel metal powder is dissolved in a sulfuric acid solution with hydrogen gas generated.

Patent Literature 1 discloses a method for producing water-soluble nickel sulfate, by heating a

green nickel oxide powder having a specific gravity of higher than 6.30 in sulfuric acid and then

performing leaching with hot water. In Patent Literature 1, examples of sulfuric acid used in the

heat treatment include a sulfuric acid solution having a concentration of 30% to 60% (Claims 1 to

) and concentrated sulfuric acid having a concentration of 95% (Claims 6 and 7). The use of

the concentrated sulfuric acid having a concentration of 95% (Examples 7 to 9) in Patent Literature

1 needs a high temperature of 275°C or higher.

Citation List

Patent Literature

[0005] Patent Literature 1: US 3002814

Summary of Invention

Technical Problem

[0006] An object of the present invention is to provide a residue processing method capable of

efficiently treating a residue including a nickel content and iron oxide, and a sulfatizing roasting

method using the same.

Solution to Problem

[0007] A first aspect of the present invention is a residue processing method including: applying

centrifugal force to a residue including a nickel content and an iron oxide to separate the nickel

content and the iron oxide.

[0008] A second aspect of the present invention is the residue processing method of the first

aspect, in which an average particle size of the nickel content and an average particle size of the

iron oxide are different from each other.

[0009] A third aspect of the present invention is the residue processing method of the first or second aspect, in which an average particle size of the nickel content is larger than an average particle size of the iron oxide.

[0010] A fourth aspect of the present invention is the residue processing method of the first to

third aspects, in which an average particle size of the residue is within a range of 50 m to 150

[m.

[0011] A fifth aspect of the present invention is the residue processing method of first to fourth

aspects, in which the residue is obtained from sulfation roasting in which an oxygen partial

pressure and a sulfur dioxide partial pressure are set under conditions in which nickel sulfate is

more thermodynamically stable than nickel oxide in an Ni-S-O system, and iron oxide is more

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

[0012] A sixth aspect of the present invention is the residue processing method of the first to

fifth aspects, in which the nickel content obtained by separating the iron oxide from the residue is

treated in a sulfation roasting furnace.

[0013] A seventh aspect of the present invention is the residue processing method of the sixth

aspect, in which the nickel content obtained by separating the iron oxide from the residue is

supplied to the sulfation roasting furnace in a slurry state.

[0014] An eighth aspect of the present invention is the residue processing method of the sixth

aspect, in which the nickel content obtained by separating the iron oxide from the residue is dried

and supplied to the sulfation roasting furnace.

[0015] A ninth aspect of the present invention is the residue processing method of the eighth

by exhaust heat from the sulfation roasting furnace.

[0016] A tenth aspect of the present invention is the residue processing method of the sixth to

ninth aspects, in which in the sulfation roasting furnace, an oxygen partial pressure and a sulfur

dioxide partial pressure are set under conditions in which nickel sulfate is more

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

[0017] An eleventh aspect of the present invention is a sulfatizing roasting method including:

a roasting step of treating a nickel-containing raw material including an iron content in a sulfation

roasting furnace, an extraction step of extracting a nickel sulfate compound from a roasted product

obtained in the roasting step, a residue processing step of treating a residue obtained after

extracting the nickel sulfate compound in the extraction step by the residue processing method of

the first to tenth aspects to separate a nickel content and an iron oxide, and a reuse step of supplying

the nickel content obtained in the residue processing step to the sulfation roasting furnace used in

the roasting step.

Advantageous Effects of Invention

[0018] According to the first aspect, since a specific gravity of iron oxide is greater than a

specific gravity of the nickel content, centrifugal force is applied to the residue including the nickel

content and iron oxide, and thus, the nickel content and the iron oxide can be efficiently separated.

[0019] According to the second aspect, even when the average particle size of the nickel content

and the average particle size of the iron oxide are different, the nickel content and iron oxide can

be efficiently separated by centrifugal force.

[0020] According to the third aspect, even when the average particle size of the nickel content

is larger than the average particle size of iron oxide, the nickel content and the iron oxide can be

efficiently separated by centrifugal force.

[0021] According to the fourth aspect, even when the average particle size of the residue is

within a range of 50 m to 150 mi, the nickel content and iron oxide can be efficiently separated.

[0022] According to the fifth aspect, since in the sulfation roasting, the nickel content of the

raw material is converted into nickel sulfate and conversion of the iron content into iron sulfate is

suppressed, consumption of the sulfur content by the iron content can be suppressed and

production efficiency of nickel sulfate can be improved.

[0023] According to the sixth aspect, the nickel content obtained by separating iron oxide from

the residue can be converted into nickel sulfate and effectively utilized.

[0024] According to the seventh aspect, by supplying the nickel content to the sulfation roasting

furnace in a slurry state, it is easy to transport the nickel content and water vapor can be generated

in the sulfation roasting furnace, and thus, a sulfur source present in the sulfation roasting furnace

is oxidized to improve efficiency of generating a sulfur oxide required for the sulfation roasting.

[0025] According to the eighth aspect, by drying the nickel content and supplying it to the

sulfation roasting furnace, a weight of the nickel content is reduced during transportation to reduce

a loss.

[0026] According to the ninth aspect, by drying the nickel content by the exhaust heat from the

sulfation roasting furnace, an energy recovery rate can be improved.

[0027] According to the tenth aspect, since the nickel content of the residue is converted into

nickel sulfate and the conversion of the iron content into iron sulfate is suppressed, the

consumption of the sulfur content by the iron content can be suppressed and the production

efficiency of nickel sulfate can be improved. Further, since the nickel content derived from the

residue is in the form of fine powder at the stage of the residue, the conversion reaction is efficient

and the treatment becomes easy even in the sulfation roasting.

[0028] According to the eleventh aspect, by applying centrifugal force to the residue after

extracting the nickel sulfate compound from the roasted product of the nickel-containing raw

material, the nickel content and iron oxide can be efficiently separated. Further, by reusing the

recovered nickel content as at least a part of the nickel-containing raw material, a yield of the

sulfation roasting of the nickel-containing raw material can be improved.

Brief Description of Drawings

[0029] FIG. 1 illustrates a configuration diagram of a sulfatizing roasting method using a

residue processing method of an embodiment.

FIG. 2 illustrates a conceptual phase diagram of an Ni-S-O system and an Fe-S-O system.

Description of Embodiments

[0030] In a sulfatizing roasting method using a residue processing method of the present

embodiment, an object to be roasted is roasted in a roasting furnace to obtain a roasted product.

Examples of the object to be roasted include nickel-containing raw materials. The roasted

product includes a sulfate such as nickel sulfate.

[0031] The nickel-containing raw material may be a nickel compound or metal nickel as long

as it contains element nickel. Examples of the nickel compound include, though not particularly

limited to, nickel salts such as nickel oxide, nickel hydroxide, nickel sulfide, and nickel chloride.

The nickel compound may be a hydrate. The metal nickel may be a nickel alloy, such as

ferronickel. When metallic nickel (a simple substance or an alloy) is used as the nickel

containing raw material, metal nickel may be, for example, a shot formed by making molten metal

into small pieces. Nickel ore can also be used as the nickel-containing raw material. Examples

of the nickel ore include one or more of nickel oxide ore, nickel sulfide ore and the like. Nickel

matte containing nickel sulfide as a main component and the like can also be used as the nickel

containing raw material.

[0032] Examples of the nickel matte include a nickel matte having a composition (by weight

ratio) of 45% to 55% of Ni, about 20% of Fe, 20% to 25% of S, and about 1% or less of Co.

Examples of the nickel matte having a nickel concentration increased in a converter include a

nickel matte having a composition (by weight ratio) of about 78% of Ni, about 1% of Co, about

1%ofFe,andabout20%ofS. This nickel matte is in a state in which Ni3 S 2 and metal nickel

(Ni) are mixed, from the amount of a sulfur content. Examples of ferronickel include a

ferronickel having a composition (by weight ratio) of 18% to 23% of Ni, about 1% of Co, and

76% to 81% of Fe.

[0033] Examples of the nickel oxide ore include laterite ore including a nickel content such as limonite and saprolite. Limonite may be a limonite including a low iron content or a limonite including a high iron content, and saprolite may be a saprolite including a high nickel content (for example, an Ni content of 1.8 wt% or more) or a saprolite including a low nickel content (for example, an Ni content of less than 1.8 wt%). Examples of the nickel sulfide ore include iron nickel sulfide ore (pentlandite ore), millerite, chalcopyrite including a nickel content, pyrrhotite including a nickel content, and the like.

[0034] The nickel-containing raw material in a roasting step preferably includes one or more

selected from the group consisting of nickel sulfide ore, nickel oxide ore, nickel sulfides, nickel

matte, nickel oxide, and ferronickel. The nickel-containing raw material does not need to include

an iron content, but in many cases, the iron content is present together with a nickel content. The

iron content is separated from a nickel sulfate compound in a post-process, but from the view point

of energy consumption, a lower iron content in the raw material is more desired. Treatment is

possible even in the case in which the iron content is higher than the nickel content, but it is

preferred that the iron content is lower than the nickel content. The nickel-containing raw

material may be used alone or in combination of two or more. When two or more nickel

containing raw materials are used, the raw materials may be supplied in the form of a mixture or

may be supplied separately. When the nickel-containing raw material is subjected to sulfation

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

nickel-containing raw material including a sulfur content as at least a part of the raw material, for

example, nickel sulfide ore, a nickel sulfide, nickel matte, and the like may be used.

[0035] Prior to the roasting step, the particle size of the nickel-containing raw material is

preferably reduced by an operation such as chopping, pulverization, and abrasion. Since a

reaction in the roasting step is initiated from a surface of the nickel-containing raw material, a

smaller particle size of the nickel-containing raw material results in a shorter reaction time, which

is preferred. A pulverization means for the nickel-containing raw material may be, though not

particularly limited thereto, one or two or more of a ball mill, a rod mill, a hammer mill, a fluid energy mill, a vibrating mill, and the like. A particle size of the nickel-containing raw material after pulverization is not particularly limited. When the nickel-containing raw material is available in the form of fine particles like limonite ore, the nickel-containing raw material may be supplied to the roasting step as it is.

[0036] Before performing a sulfation roasting step of the present embodiment, an oxidation

roasting step may be provided, for the purpose of oxidizing an iron content, a sulfur content, and

the like in the nickel-containing raw material. In the oxidation roasting step, 02 gas or the like

may be supplied as an oxidizing agent. The oxidation roasting step may be carried out in the

same roasting furnace as the sulfation roasting step, or an oxidation roasting furnace different from

a sulfation roasting furnace may be provided. When another oxidation roasting furnace is

provided, a roasted product of the oxidation roasting furnace may be supplied to the sulfation

roasting furnace as a raw material.

[0037] Examples of the roasting furnace for performing sulfation roasting include a stirring

type roasting furnace, a rotary furnace type roasting furnace, a fluidized roasting furnace having a

fluidized bed, and the like. Regarding roasting of the ore and the like, conventionally, after

coarsely pulverizing mined ore, sulfation roasting using a stirring type roasting furnace or a rotary

furnace type roasting furnace is performed. In this case, a burden of pretreating an object to be

roasted is small and a rotation speed is slow, but a reaction speed is slow and an apparatus becomes

large. Thus, a fluidized roasting furnace has become widespread, in which the object to be

roasted is roasted while flowing in a floated state in combustion air. The apparatus can be

miniaturized by adopting the fluidized roasting furnace.

[0038] The sulfatizing roasting method of the present embodiment includes: a roasting step of

treating a nickel-containing raw material including an iron content in a sulfation roasting furnace,

an extraction step of extracting a nickel sulfate compound from a roasted product obtained in the

roasting step, a residue processing step of treating a residue obtained after extracting the nickel

sulfate compound in the extraction step by the residue processing method of the present embodiment to separate a nickel content and iron oxide, and a reuse step of supplying the nickel content obtained in the residue processing step to the sulfation roasting furnace used in the roasting step.

[0039] FIG. 1 illustrates a schematic configuration of a system which performs the sulfatizing

roasting method using the residue processing method according to the present embodiment. The

treatment system of the present embodiment includes a sulfation roasting furnace 10 for carrying

out the roasting step, a dissolution tank 20 and a solid-liquid separation tank 30 for carrying out

the extraction step, and a separator 40 for carrying out the residue processing method. A nickel

content 42 obtained by the separator 40 can be supplied to the sulfation roasting furnace 10,

thereby being reused for sulfation roasting.

[0040] In the sulfation roasting furnace 10, a raw material 11 including a nickel-containing raw

material is treated by sulfation roasting to convert the nickel content in the nickel-containing raw

material into nickel sulfate. The raw material 11 supplied to the sulfation roasting furnace 10

may include a sulfur content which is insufficient for the nickel-containing raw material, oxygen

for oxidizing the sulfur content, and the like. In FIG. 1, for simplicity, supply routes of the

respective raw materials 11 are not distinguished. An auxiliary substance or material may be

supplied to the sulfation roasting furnace 10 for the purpose of improving the conversion efficiency

of the sulfation roasting, together with the raw material 11.

[0041] The sulfation roasting step gives a roasted product 12 including a nickel sulfate

compound. A dissolved product 22 including the nickel sulfate compound is obtained through a

water dissolution step of dissolving the nickel sulfate compound in water, by supplying water 21

to the roasted product 12 in the dissolution tank 20. As will be described in detail later, it is

preferred to cool the roasted product 12 in a cooling section 13 before adding the water 21 to the

roasted product 12. Alternatively, the roasted product 12 may be pulverized before adding the

water 21 to the roasted product 12. Since the iron content in the roasted product 12 is in a state

of being sparingly soluble in water, such as iron oxide and iron sulfide, the dissolved product 22 includes a solid phase. Therefore, by separating the dissolved product 22 into a solid phase and a liquid phase in the solid-liquid separation tank 30, a nickel sulfate solution 31 is obtained as the liquid phase, and a residue 32 including iron oxide is separated as the solid phase. Further, if necessary, for example, a purification step of the nickel sulfate solution 31 can be performed, for separating nickel sulfate and cobalt sulfate or the like, thereby obtaining a nickel sulfate compound from which impurities such as cobalt have been removed.

[0042] The residue 32 includes a nickel content and iron oxide. By applying centrifugal force

to the residue 32, the nickel content and the iron oxide can be separated. Since the specific

gravity of iron oxide is greater than the specific gravity of the nickel content, the nickel content

and iron oxide can be efficiently separated. The average particle size of the nickel content and

the average particle size of iron oxide included in the residue 32 maybe different. Inthesulfation

roasting described above, iron oxide tends to become fine. Therefore, the average particle size

of the nickel content may be larger than the average particle size of iron oxide. The average

particle size of the residue 32 is, for example, within a range of 50 m to 150 [m. The nickel

content is a component of the nickel-containing raw material which has not been converted into

nickel sulfate, and is, for example, a sulfide or oxide of nickel. Examples of iron oxide include

Fe 20 3, FeO, and Fe304.

[0043] In the present embodiment, the separator 40 is provided for separating the residue 32.

Examples of the separator 40 or a separation method thereof include a cyclone, a centrifuge, and

a centrifugal filtration. Examples of the cyclone include a gas cyclone using a gas as a fluid, a

liquid cyclone using a liquid as a fluid, and a hydrocyclone using water as a fluid. Since water

has a small difference in specific gravity from the residue 32 and costs less, it is preferred to use

water as the fluid. It is preferred that water is added to the residue 32 and pumped by a pump 33

to supply the residue 32 to the separator 40 as a residue liquid 34 dispersed in water. The residue

liquid 34 may include the residue 32 in a slurry form. In order to stabilize a concentration of the

residue included in the residue liquid 34, a pipe circulating in a loop shape is provided between the solid-liquid separation tank 30 and the pump 33, and a part of the residue or water included in the residue liquid 34 may be returned to the solid-liquid separation tank 30. When a gas is used as the fluid, the solid-phase fine powder residue 32 may be directly supplied to the separator 40.

[0044] In the separator 40, iron oxide 41 and a nickel content 42 are separated. The particle

size as a reference (classification point) when the iron oxide 41 and the nickel content 42 are

separated in the separator 40 is preferably about 100 to 150 m. Examples of the classification

points (separation limit particle size) between coarse powder having a large particle size and fine

powder having a small particle size include a specific particle size, such as a 50% separation

particle size, an equilibrium particle size (particle size in which the coarse powder and the fine

powder have the same mass), a minimum particle size in the coarse powder, and a maximum

particle size in the fine powder. For example, particles larger than 100 m may be the nickel

content 42, and particles smaller than 100 m maybe the iron oxide 41. The inner surface of the

separator 40 preferably has improved wear resistance by soft rubber or the like.

[0045] The separator 40 may be provided in one stage, or may be provided in two or more

stages in series, for example, by providing the separator 40 having a small classification point next

to the separator 40 having a large classification point. In order to improve the processing

capacity of the separator 40, a plurality of separators 40 may be provided in parallel, and a path of

the residue liquid 34 supplied from the solid-liquid separation tank 30 or the pump 33 may be

branched toward the plurality of separators 40.

[0046] The nickel content 42 after being separated from the iron oxide 41 can be supplied to

the sulfation roasting furnace 10 for treatment. As a result, the nickel content in the residue 32

can be effectively utilized. When the nickel content 42 is returned to the sulfation roasting

furnace 10, if the nickel content 42 is dispersed in the liquid, it may be returned to the sulfation

roasting furnace 10 as it is. Further, a nickel content 44 may be supplied to the sulfation roasting

furnace 10 after being treated by a treatment apparatus 43. Examples of the treatment apparatus

43 include, when the nickel content 42 after separation is dispersed in a gas, an apparatus which disperses the nickel content 42 in water to form a slurry, or when the nickel content 42 after separation is dispersed in a liquid such as water, a drying apparatus which dries the nickel content

42. When the nickel content 42 is formed into a slurry in the treatment apparatus 43, the nickel

content 44 supplied to the sulfation roasting furnace 10 becomes a slurry. When the nickel

content 42 is dried in the treatment apparatus 43, the nickel content 44 supplied to the sulfation

roasting furnace 10 is in a dry state.

[0047] In the sulfation roasting furnace 10, it is not necessary to perform treatment by a

hydrometallurgic method using liquid sulfuric acid, and nickel sulfate (NiS0 4 ) can be obtained as

the roasted product 12 by a pyrometallurgic method. S02 is generated as a gas by burning the

sulfur content in the raw material 11 or the sulfur content supplied from the outside and is brought

into contact with the nickel content in the raw material 11 to produce nickel sulfate. For example,

when a nickel matte including Ni3 S 2 and Ni is subjected to sulfation roasting, the reaction formula

between an external sulfur content (S) and oxygen (02) is as follows.

[0048] S (solid) + 02 (gas) -- SO 2 (gas)

Ni3S2 (solid) + 502 (gas) + S02 (gas) -- 3NiSO4 (solid)

Ni (solid) + S02 (gas) + 02 (gas) -- NiS04 (solid)

[0049] It is considered that when S02 gas comes into contact with the surface of the particles,

the salt of NiS04 is precipitated on the surface of the particles to proceed with the reaction. The

volume of NiSO 4 precipitated at this time is larger than thatof Ni3S2. Furthermore, the S02 gas

is diffused through voids produced by the precipitation of NiSO 4 , thereby proceeding with the

sulfation roasting ofNi 3 S2 inside. Asa result of conversion of Ni3S2 into NiSO 4 to cause volume

expansion of the nickel content, the particles are broken and leave a residue having a smaller

particle size. The finer the particle size of the raw material 11, the faster the conversion into

NiSO4 , but the nickel matte is hard, so that the energy required for pulverization is higher. The

pulverization operation has a problem of time and energy, and has restrictions or limitations in

preparing a nickel matte raw material having a small particle size. Further, as described above, after an NiSO 4 coat is produced on the surface of the raw material particles, the diffusion of SO 2 gas becomes rate-determining, and the efficiency of the conversion reaction is decreased.

Therefore, in making the conversion rate of NiSO4 100% in one sulfation roasting step, it is not

easy to extend a residence time in the roasting furnace, and the productivity is also decreased.

Therefore, from the viewpoint of economics, the conversion rate should be kept within a certain

range, and thus, it is efficient that nickel sulfate, which is easily dissolved from the roasted product

12, is dissolved in the dissolution tank 20, and then the residue 32 is subjected to sulfation roasting

again. However, iron oxide produced by oxidizing the iron content in the raw material 11 is

incorporated in the residue 32. Therefore, it is desirable to supply the nickel contents 42 and 44

obtained by separating the iron oxide 41 from the residue 32 to the sulfation roasting furnace 10.

[0050] Regarding the iron oxide included in the residue 32, the fine particles of the raw material

11 are generated with cracks under the circumstances described above, and thus the iron oxide is

formed ofultrafine particles having a very small particle size and is generally difficult to be filtered.

There are various filtration methods, but in order to adopt, for example, filtration under reduced

pressure, vacuum filtration, and the like, it is difficult to separate the nickel content without using

a filtration aid. Therefore, by applying centrifugal force to the residue 32 in the separator 40 to

separate the nickel content and iron oxide, the iron oxide 41 and the nickel content 42 can be easily

separated.

[0051] When the nickel contents 42 and 44 are supplied to the sulfation roasting furnace 10, if

the nickel contents 42 and 44 are in a slurry form, the nickel contents 42 and 44 can be easily

transported, and also water vapor can be generated inside the sulfation roasting furnace 10.

Therefore, the efficiency of generating a sulfur oxide required for sulfation roasting from a sulfur

source by oxidation is improved. When the nickel contents 42 and 44 are supplied to the

sulfation roasting furnace 10, if the nickel contents 42 and 44 are in a dry state, the weights of the

nickel contents 42 and 44 can be reduced during transportation to reduce a loss.

[0052] When the nickel contents 42 and 44 are dried, it is also possible to dry them by the exhaust heat from the sulfation roasting furnace 10. As a result, the energy recovery rate can be improved. As a method of transporting the exhaust heat from the sulfation roasting furnace 10 to the treatment apparatus 43 for drying the nickel content 42, a transport pipe for a heat medium such as hot water or steam or a heat transport path such as a heat pipe (not shown) may be connected to the sulfation roasting furnace 10. Alternatively, the exhaust heat from the sulfation roasting furnace 10 is accumulated in the heat storage material as latent heat of a phase change or the like, and the heat-stored heat storage material can be transported to the treatment apparatus 43 and used for drying.

[0053] After the sulfation roasting step and the water dissolution step, the ratio between the

nickel content included in the nickel sulfate solution 31 and the nickel content included in the

residue 32 is not particularly limited, but even in the case in which the nickel content included in

the residue 32 is several % to tens of percent, the nickel content included in the residue 32 is

separated from the iron content and then returned to the sulfation roasting furnace 10 to continue

the treatment, thereby improving a yield of obtaining the nickel sulfate solution 31 from the nickel

content of the nickel content of the raw material 11.

[0054] The sulfation roasting furnace 10 which is the discharge source of the residue 32 and the

sulfation roasting furnace 10 which is the supply point of the nickel contents 42 and 44 separated

from the residue 32 may be the same sulfation roasting furnace 10 or sulfation roasting furnaces

different from each other. For any of the sulfation roasting furnaces 10, it is preferred to carry

out a sulfatizing roasting method for obtaining nickel sulfate from a nickel-containing raw material

including an iron content under predetermined conditions. Next, preferred conditions of the

sulfatizing roasting method will be described in more detail. The nickel content in the sulfation

roasting step includes the nickel content in the nickel-containing raw material of the raw material

11 and the nickel contents 42 and 44 separated from the residue 32.

[0055] In the sulfation roasting of the nickel-containing raw material, it is preferred that an

oxygen partial pressure and a sulfur dioxide partial pressure are set under conditions in which nickel sulfate is more thermodynamically stable than nickel oxide in an Ni-S-0 system, and iron oxide is more thermodynamically stable than iron sulfate in an Fe-S-0 system. As a result, even when the nickel-containing raw material has an iron content, a nickel content is converted into nickel sulfate while the conversion from the iron content into iron sulfate is suppressed, thereby suppressing consumption of a sulfur content by the iron content and improving efficiency of producing nickel sulfate.

[0056] FIG. 2 is an example of a conceptual phase diagram of an Ni-S-0 system and an Fe-S

o system. The boundary lines between phases in the Ni-S-0 system are denoted by dashed lines

(-----), and the boundary lines between phases in the Fe-S-0 system are denoted by dash-dotted

lines (- ---- ). The chemical formulas along with the arrows each represent a thermodynamically

stable phase in the side from each boundary line towards the arrow. The horizontal axis of the

phase diagram illustrated in FIG. 2 represents the logarithm of the 02 partial pressure. The 02

partial pressure increases toward the right side, and the 02 partial pressure decreases toward the

left side. The vertical axis of the phase diagram illustrated in FIG. 2 represents the logarithm of

the S02 partial pressure. The S02 partial pressure increases toward the upper side, and the S02

partial pressure decreases toward the lower side. The unit of the partial pressure is, for example,

atmosphere (atm = 101325 Pa).

[0057] In the Ni-S-0 system, examples of nickel sulfate include NiS0 4 , and examples of nickel

oxide include NiO. In the phase diagram illustrated in FIG. 2, the boundary line LNi represents

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

in which nickel oxide is thermodynamically stable. In the region having higher S02 partial

pressure and higher 02 partial pressure than the boundary line LNi, nickel sulfate is a

thermodynamically stable phase. In the region having lower S02 partial pressure and lower 02

partial pressure than the boundary line LNi, nickel oxide is a thermodynamically stable phase.

[0058] In the Fe-S-0 system, examples of iron sulfate include FeSO 4 and Fe2(SO 4 )3, and

examples of iron oxide include Fe203. In the phase diagram illustrated in FIG. 2, the boundary line LFe represents a boundary line between a region in which iron sulfate is thermodynamically stable and a region in which iron oxide is thermodynamically stable. In the region having higher

S02 partial pressure and higher 02 partial pressure than the boundary line LFe, iron sulfate is a

partial pressure than the boundary line LFe, iron oxide is a thermodynamically stable phase.

[0059] According to the phase diagram illustrated in FIG. 2, in a region A having lower S02

partial pressure and lower 02 partial pressure than the boundary line LFe and having higher S02

partial pressure and higher 02 partial pressure than the boundary line LNi, nickel sulfate is a

thermodynamically stable phase in the Ni-S-0 system, and iron oxide is a thermodynamically

stable phase in the Fe-S-0 system. Thus, roasting a system including nickel (Ni), oxygen (0),

and sulfur (S) under the conditions of the overlapping region A can convert a nickel content into

nickel sulfate while suppressing production of iron sulfate even when the system has an iron

content.

[0060] In the sulfation roasting step of the present embodiment, a roasting temperature

(sulfation roasting temperature) is preferably in a range of 400 to 750°C, and more preferably in

a range of 550 to 750°C. Specific examples of the sulfation roasting temperature include 400°C,

450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, or a higher, lower, or medium temperature

range. At such a roasting temperature, the reduction of an iron content is suppressed, and the

iron content in the form of iron oxide, iron sulfide, and the like may be present together with the

nickel sulfate compound, thereby suppressing coagulation of particles in the roasted product and

facilitating treatment of the post-process. Since a carbonate is decomposed at this temperature,

even in the case in which the carbonate is incorporated, the carbonate can be prevented from being

dissolved in water remaining as an impurity, thereby facilitating treatment of the post-process.

The sulfation roasting temperature is more preferably 600 to 700°C. At this

temperature, even in the case in which the object to be roasted contains manganese (Mn) as an

impurity derived from the nickel-containing raw material, manganese forms a spinel structure with iron, whereby it is easy to remove manganese as an insoluble matter.

[0061] Regarding the 02 partial pressure in the sulfation roasting step, the common logarithm

log p(O2) of the 02 partial pressure in terms of atmosphere (atm) unit is preferably in a range of

4 to -6, and depending on the conditions and the like, it is more preferred that log p(O2) is in a

range of -4 to -5, or log p(O2) is in a range of -5 to -6. As the 02 partial pressure decreases, the

SO2 partial pressure tends to increase in the overlapping region A in FIG. 2. This can promote

production of nickel sulfate while suppressing generation of iron sulfate. This optimum region

is slightly shifted depending on the sulfation roasting temperature, and as the temperature rises,

the log p(O2) in the overlapping region A moves to a larger side (closer to zero (0)). Log p(O2)

may be selected from, for example, a range of -8 or more and 0 or less, depending on the

relationship with logp(S02) and the sulfation roasting temperature.

[0062] Regarding the S02 partial pressure in the sulfation roasting step, the common logarithm

log p(S02) of the S02 partial pressure in terms of atmosphere (atm) unit is preferably in a range

of -I to +1, and log p(S02) is more preferably in a range of -I to 0. In the overlapping region A

shown in FIG. 2, the generation of the sulfate can be promoted by increasing the S02 partial

pressure. Furthermore, when the S02 partial pressure is at about normal pressure or in a lower

range (the common logarithm of the partial pressure is substantially 0 or lower), the total pressure

of the roasting atmosphere in the sulfation roasting step is not too high, and it is easy to handle the

equipment. Log p(S02) maybe selected from, for example, a range of -4 or more and +1 or less,

depending on the relationship with log p(O2) and the sulfation roasting temperature.

[0063] To maintain the 02 partial pressure low in the roasting furnace, an inert gas, such as

nitrogen (N 2 ) or argon (Ar), may be supplied to the roasting furnace. These inert gases can also

be used as a carrier for supplying a volatile component, such as gas or steam, to the roasting

furnace. The S02 partial pressure can be adjusted, for example, by controlling the supply amount

of the sulfur source. When the nickel-containing raw material has a low sulfur content, the sulfur

content may be supplied to the sulfation roasting step. Examples of the supply source of the sulfur content (sulfur source) include solid sulfur (elementary sulfur, S) which is a solid at room temperature, sulfur oxides (such as SO 2 ), sulfuric acid (H 2 SO 4 ), sulfates, sulfides, and sulfide ore such as pyrite (FeS2). When the sulfur source is sulfur (S), it is preferred to produce the SO 2 gas in an oxygen-enriched state. Sulfur may be burned in an oxygen-containing atmosphere to produce a sulfur oxide.

[0064] The preferred range of partial pressure can be obtained from the positions of the

boundary line LNi and the boundary line LFe, by examining the phase diagram described above

according to the sulfation roasting temperature. For example, when the sulfation roasting

temperature is 650 to 750°C, examples of the preferred range of partial pressure include log p(O2)

of about -8 to -4 and logp(SO2) of about -2 to +2, log p(O2) of about -3 to -2 and logp(SO2) of

about -3 to +1, and log p(O2) of about -I to 0 and log p(SO2) of about -4 to 0.

[0065] Next, the purification or the like of nickel sulfate obtained by sulfation roasting will be

described in more detail. The water 21 added to the roasted product 12 in the dissolution tank

as the water dissolution step is preferably pure water treated so as not to include impurities.

The water treatment method is not particularly limited, but may be, for example, one or more of

filtration, membrane separation, ion exchange, distillation, sterilization, chemical treatment, and

adsorption. Water for dissolution may be, for example, clean water obtained from water sources,

industrial water, or the like, or may be water obtained by treating wastewater generated in other

processes. Two or more types of water may be used. Dissolution may be performed in an acidic

sulfuric acid solution having a pH of about 4, as well as pure water. For example, in a region

which is an oxidation area in oxidation-reduction potential measurement at a pH of the solution of

about 4 to 5, for example, 3.8 to 5.5, it is advantageous for selectively extracting the nickel sulfate

compound in an aqueous phase, while suppressing the dissolution of impurities such as other

sulfates, which is thus preferred.

[0066] The solubility of nickel sulfate in water is the highest at 150°C, at which 55 g NiSO 4 is

dissolved in 100 g of the solution, but even at 0°C, 22 g NiSO4 is dissolved in 100 g of the solution.

Therefore, dissollution operation is preferably performed at a temperature equal to or lower than

the boiling point of water. It is preferred that the dissolved product 22 obtained in the water

dissolution step has a NiSO 4 concentration at which NiSO4 does not precipitate even at room

temperature, and it is more preferred that the dissolved product 22 having a higher NiSO 4

concentration is maintained in a heated state. In order to adjust the temperature of the dissolved

product 22, it is preferred to adjust the temperature of the roasted product 12 or the temperature

of the water 21 before performing the dissolution operation. The residual heat of the roasted

product 12 may be utilized as at least a part of the heat source which maintains the heated state of

the dissolved product 22. Therefore, it is preferred to set the temperature of the roasted product

12 before being dissolved in the water 21 to an appropriate temperature.

[0067] As described above, in the system illustrated in FIG. 1, the cooling section 13 is provided

between the sulfation roasting furnace 10 and the dissolution tank 20. The cooling section 13

may be a batch type or a continuous type. The batch type may have a configuration in which the

roasted product 12 is allowed to stand until the temperature drops to a desired temperature without

adding a water content. In the case of the continuous type, for example, the cooling section 13

may be provided in the pipe connecting the sulfation roasting furnace 10 and the dissolution tank

20. In the cooling section 13, for example, a heat exchanger may be provided to recover excess

residual heat from the roasted product 12, and the recovered residual heat may be used as various

heat sources.

[0068] The particles of the roasted product 12 may be solidified or a coat which is sparingly

soluble in water may be formed on the surface of the particles, due to the state of the roasted

product 12 obtained from the sulfation roasting furnace 10 or the state change during cooling in

the cooling section 13. Therefore, a process of pulverizing the roasted product 12 may be added

before adding the water 21 to the roasted product 12. A pulverization means for the roasted

product 12 may be, though not particularly limited thereto, one or two or more of a ball mill, a rod

mill, a hammer mill, a fluid energy mill, a vibrating mill, and the like. Pulverization of the roasted product 12 may be started before cooling the roasted product 12 or after cooling the roasted product 12.

[0069] The solid-liquid separation method after the water dissolution step is not particularly

limited, and examples thereof include filtration, centrifugation, and settling separation. The

solid-liquid separation tank 30 is preferably an apparatus having high performance of separating

solid-phase fine particles to be the residue 32, and examples thereof include one or two or more

of a filtration tank, a centrifugal separation tank, a settling tank, a precipitation tank, and the like.

For example, in filtration, the type of filtration is not particularly limited, and examples of the type

of filtration include gravity filtration, filtration under reduced pressure, pressure filtration,

centrifugal filtration, filtration with addition of a filtration aid, squeeze filtration, and the like.

Pressure filtration, which allows easy adjustment of differential pressure and rapid separation, is

preferred.

[0070] Examples of impurities which can be present together with the nickel sulfate compound

include iron (Fe), cobalt (Co), aluminum (Al), and the like. In the case in which salts of these

metals are sulfates in the roasting step, when the nickel sulfate compound is dissolved in water,

iron sulfate, cobalt sulfate, and the like are also dissolved. Furthermore, for example, iron is

precipitated in water as an oxide such as FeOOH, Fe 20 3, and Fe304, or the like, and it is easy to

remove impurities from the nickel sulfate compound. Since the conditions for the sulfation

roasting step in the present embodiment is set to conditions under which iron is unlikely to form

iron sulfate, the nickel sulfate solution 31 including a low iron content is obtained by the water

dissolution and the solid-liquid separation. The residue 32 including iron oxide and the like after

separating the nickel sulfate solution 31 can also be reused as an iron content in cement. Further,

the iron oxide 41 separated from the residue 32 can be used for the production of pig iron or the

like as a raw material for iron manufacture using a melting-reduction furnace, an electric furnace,

or the like, or for pigments, ferrites, magnetic materials, sintered materials, and the like. In

particular, when the area where the nickel-containing raw material is produced is a remote area away from industrial areas, cities, and the like, it is advantageous to commercialize the iron content locally like the nickel content from the viewpoint of transportation costs. For example, if the pig iron is produced using an electric furnace provided in a smelting process of ferronickel and the volume is reduced, it will be easy to carry out iron as unprocessed iron metal.

[0071] Since among the impurities, metals having lower ionization tendency than hydrogen (H),

such as copper (Cu), gold (Au), silver (Ag), and platinum-group metals (PGM), remain as solid in

the water dissolution step, the metals can be removed by the solid-liquid separation step. The

solid removed by the solid-liquid separation step may include compounds such as As, Pb, and Zn,

in addition to the above impurities. The solid including these impurities can be recycled as

valuables.

[0072] Since the nickel sulfate solution 31 obtained by the water dissolution and the solid-liquid

separation includes the nickel sulfate compound as a main component, it can be transported and

used as the solution of the nickel sulfate compound without any processing, or as a solid of the

nickel sulfate compound by drying or the like. In the case in which it is preferred to reduce the

amount of, for example, cobalt sulfate and the like, as the impurities in the nickel sulfate solution

31, depending on the application, techniques such as solvent extraction, electrodialysis,

electrowinning, electrorefining, ion exchange, and crystallization can be used.

[0073] Solvent extraction preferably uses an extractant capable of preferentially or selectively

extracting cobalt rather than nickel in a solvent. Thus, the nickel sulfate compound remains in

the aqueous solution to allow efficient purification. Examples of the extractant include organic

compounds having a functional group capable of being bonded to a metal ion such as a phosphinic

acid group or a thiophosphinic acid group. In solvent extraction, an organic solvent capable of

separating the extractant from water may be used as a diluent. By dissolving the extractant

bonded to a metal ion such as cobalt ion in a diluent, it is easy to separate impurities from an

aqueous solution containing the nickel sulfate compound without using a large amount of the

extractant. The diluent is preferably an organic solvent which is difficult to be miscible with water.

[0074] In crystallization, the nickel sulfate compound of interest may be crystallized from the

solution by at least one factor of a change in temperature, a decrease in solvent volume, addition

of other substances, and the like. In this case, at least a part of impurities remains in the liquid

phase to allow purification. Specific examples include evaporation crystallization and poor

solvent crystallization. The evaporation crystallization involves concentrating the solution by

boiling or evaporation under reduced pressure to crystallize the nickel sulfate compound. The

poor solvent crystallization is a crystallization method used in pharmaceutical manufacturing and

involves, for example, adding an organic solvent to a solution containing the nickel sulfate

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

is preferably an organic solvent miscible with water, and examples thereof include at least one

selected from the group consisting of methanol, ethanol, propanol, isopropanol, butyl alcohol,

ethylene glycol, and acetone. Two or more organic solvents may be used. For a concentration

range in which the organic solvent is miscible with water, it is preferred that the organic solvent is

miscible at a concentration where the organic solvent is added to the extent that the nickel sulfate

compound precipitates, and it is more preferred that the organic solvent is freely miscible at an

any ratio. The organic solvent added in the crystallization step is not limited to an anhydrous

organic solvent and may be an organic solvent containing water to the extent that water does not

hinder crystallization. A ratio between water and the organic solvent is not particularly limited,

but may be set, for example, in a range of 1:20 to 20:1, and a ratio of about 1:1, for example, 1:2

to 2:1 is preferred.

[0075] When the solid nickel sulfate compound is obtained after crystallization or the like, the

nickel sulfate compound may be in the form of anhydride, monohydrate, dihydrate, pentahydrate,

hexahydrate, or heptahydrate of nickel sulfate. The nickel sulfate compound precipitated by

crystallization can be separated from the solution by solid-liquid separation. The solid-liquid

separation method is not particularly limited, but examples thereof include filtration, centrifugation, settling separation, and the like. It is preferred that the metals dissolved in the solution are neutralized and removed from the solution by precipitation or other methods. When the cleaned solution is mainly composed of a mixture of water and the organic solvent, water and the organic solvent can be separated from each other by distillation or other methods.

[0076] According to the sulfatizing roasting method of the present embodiment, the following

effects can be obtained:

(1) The yield of the nickel sulfate compound can be improved by effectively utilizing

the nickel content in the residue.

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

can be accelerated to improve reactivity.

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

raw material by sulfation roasting.

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

Generation of hydrogen (H 2 ) gas can also be suppressed.

(5) In the roasted product, an iron content is a chemical species which is sparingly

soluble in water and a nickel content is easily dissolved in water as a nickel sulfate compound,

and thus, it easy to remove the iron content from the roasted product.

(6) The facility cost can be reduced as compared with the conventional method.

(7) Since the conversion reaction of the nickel-containing raw material can be promoted,

for example, when iron is supplied in the form of iron oxide, the conversion reaction proceeds

without giving an opportunity for iron oxide to form iron sulfate and to form an iron-nickel ferrite

alloy. Therefore, a roasted product containing high-purity nickel sulfate can be obtained.

[0077] Hereinabove, the present invention is described on the basis of preferred embodiments,

but the present invention is not limited to the above embodiments, and various modifications are

possible without departing from the spirit of the present invention.

[0078] The object to be roasted is not limited to the nickel-containing raw material, but may be a raw material containing a metal other than nickel (Cu, Zn, Co, Fe, or the like). It is also possible to apply the roasting of the nickel-containing raw material according to the embodiment described above to the roasting for obtaining the metal compound from raw materials containing other metals.

[0079] The residue processing method described above can also be used for treating residues

discharged from a process other than the sulfation roasting.

Examples

[0080] <Experimental Examples>

An iron-containing nickel matte (Ni3 S2) was roasted in sulfation roasting test equipment.

The roasting conditions were a roasting temperature of 650°C, log p(O2) of -2.0, and logp(S02)

of -2.0. The obtained roasted product was dissolved in pure water at a temperature of 80°C.

The obtained dissolved product was allowed to stand for 1 hour, and the residue including the

nickel sulfate solution of the supernatant and iron oxide was separated by a filtration device using

MILLIPORE (registered trademark). The residue remaining on the filtration membrane was

dried in a thermostatic chamber at 110°C for 2 hours, and the average particle size was measured

with a Luzex (registered trademark) image analysis type particle size distribution measuring

device available from Nireco Corporation. As a result, the average particle size (p50) was 100

to 150 [m. Further, as a result of analyzing the dried product with an electron probe

microanalyzer (EPMA), a fraction on the side having a large particle size was a nickel content and

a fraction on the side having a small particle size was iron oxide.

[0081] From the prereview of the phase diagrams of the Ni-S-O system and the Fe-S-O system,

it was considered that the condition that log p(O2) was -2.0 and log p(S02) was -2.0 at a roasting

temperature of 650°C was appropriate for conversion into NiSO 4 .

[0082] <Example 1>

The nickel matte was sulfated and roasted under the same conditions as in the above

experimental example to obtain a roasted product, which was dissolved in pure water at a temperature of 80°C. The obtained dissolved product was allowed to stand for 1 hour, and the residue including the nickel sulfate solution of the supernatant and iron oxide was separated by a filtration device using MILLIPORE (registered trademark). The residue remaining on the filtration membrane was dispersed in pure water to obtain a residue dispersion. Apumppressure

(discharge pressure) was 1.0 kgf/cm 2, and a throughput when the residue dispersion was provided

to a cyclone (hydrocyclone manufactured by Rasa Industries, Ltd.: Super-150-Cyclone was used

alone) at a flow velocity of 38.0 L/min was 2.2 m3/h. The pump pressure was changed to change

the amount of residue dispersion supplied to the cyclone, and the throughput was changed as

shown in Table 1. In addition, 1 kgf/cm2 is 9.80665 N/cm 2 , that is, 98066.5 Pa.

[0083] [Table 1]

One cyclone

Pump pressure Flow velocity Throughput Separation efficiency

(kgf/cm 2 ) (L/min) (m 3 /h) (%)

1.0 38.0 2.2 97 to 98

2.0 60.0 3.6 96 to 98

3.0 75.0 4.5 94 to 97

4.0 90.0 5.4 93 to 97

[0084] <Example 2>

A residue dispersion was obtained in the same manner as in Example 1. A pump

pressure (discharge pressure) was 1.0 kgf/cm 2, and a throughput when the residue dispersion was

provided to a cyclone (hydrocyclone manufactured by Rasa Industries, Ltd.: 6 sets of Super-150

Cyclones in parallel were used) at a flow velocity of 228 L/min was 13.6 m3/h. The pump

pressure was changed to change the amount of residue dispersion supplied to the cyclone, and the

throughput was changed as shown in Table 2.

[0085] [Table 2]

6 sets of cyclones

Pump pressure Flow velocity Throughput Separation efficiency

(kgf/cm 2 ) (L/min) (m3 /h) (%)

1.0 228 13.6 97 to 98

2.0 360 21.6 96 to 98

3.0 450 27.0 94 to 97

4.0 540 32.4 93 to 97

[0086] In Tables 1 and 2, the separation efficiency (%) is the weight ratio of a nickel content

with respect to 100% of the total of the iron oxide and the nickel content recovered from the

cyclone. Iron oxide having a small particle size was separated above the center of the cyclone,

and the nickel content having a large particle size was separated below the peripheral wall part of

the cyclone. When the throughput of the cyclone was large, the fluctuation width of separation

efficiency became slightly larger.

Industrial Applicability

[0087] The present invention can be used to manufacture a high-purity nickel sulfate compound

which is useful as raw materials of various nickel compounds and metal nickel used in electric

components such as a secondary battery, chemical products, and the like.

Reference Signs List

[0088] 10 Sulfation roasting furnace

11 Raw material

12 Roasted product

13 Cooling section

Dissolution tank

21 Water

22 Dissolved product

Solid-liquid separation tank

31 Nickel sulfate solution

32 Residue

33 Pump

34 Residue liquid

Separator

41 Iron oxide

42,44 Nickel content

43 Treatment apparatus

Claims

1. A residue processing method comprising:

applying centrifugal force to a residue including a nickel content and an iron oxide to

separate the nickel content and the iron oxide.

2. The residue processing method according to claim 1, wherein

an average particle size of the nickel content and an average particle size of the iron

oxide are different from each other.

3. The residue processing method according to claim 1 or 2, wherein

an average particle size of the nickel content is larger than an average particle size of

the iron oxide.

4. The residue processing method according to any one of claims I to 3, wherein

an average particle size of the residue is within a range of 50 m to 150 [m.

5. The residue processing method according to any one of claims 1 to 4, wherein

the residue is obtained from sulfation roasting in which an oxygen partial pressure and

a sulfur dioxide partial pressure are set under conditions in which nickel sulfate is more

thermodynamically stable than nickel oxide in an Ni-S-O system, and iron oxide is more

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

6. The residue processing method according to any one of claims I to 5, wherein

the nickel content obtained by separating the iron oxide from the residue is treated in a

sulfation roasting furnace.

7. The residue processing method according to claim 6, wherein

the nickel content obtained by separating the iron oxide from the residue is supplied to

the sulfation roasting furnace in a slurry state.

8. The residue processing method according to claim 6, wherein

the nickel content obtained by separating the iron oxide from the residue is dried and

supplied to the sulfation roasting furnace.

9. The residue processing method according to claim 8, wherein

the nickel content obtained by separating the iron oxide from the residue is dried by

exhaust heat from the sulfation roasting furnace.

10. The residue processing method according to any one of claims 6 to 9, wherein

in the sulfation roasting furnace, an oxygen partial pressure and a sulfur dioxide partial

pressure are set under conditions in which nickel sulfate is more thermodynamically stable than

nickel oxide in an Ni-S-O system, and iron oxide is more thermodynamically stable than iron

sulfate in an Fe-S-O system.

11. A sulfatizing roasting method comprising:

a roasting step of treating a nickel-containing raw material including an iron content in

a sulfation roasting furnace;

an extraction step of extracting a nickel sulfate compound from a roasted product

obtained in the roasting step;

a residue processing step of treating a residue obtained after extracting the nickel sulfate

compound in the extraction step by the residue processing method according to any one of claims

1 to 10 to separate a nickel content and an iron oxide; and a reuse step of supplying the nickel content obtained in the residue processing step to the sulfation roasting furnace used in the roasting step.