AU2018445145A1 - Method and device for processing nickel oxide ore - Google Patents

Abstract

A method for processing nickel oxide ore, the method having an oxidation roasting step for converting FeOOH included in nickel oxide ore to Fe

Description

DESCRIPTION METHOD AND DEVICE FOR PROCESSING NICKEL OXIDE ORE

Technical Field

[0001] The present invention relates to a method and device for processing nickel oxide ore.

Background Art

[0002] Laterite ore produced in a tropical or subtropical area, such as limonite or saprolite, is

known as nickel oxide ore. Saprolite is formed in a process of formation of clay ore by rock

weathering, and is located on a rock under soil mainly composed of leaf mold and limonite. In

the tropical area, silica and bases are leached during the rock weathering, and metal elements such

as iron (Fe) and nickel (Ni) are concentrated in saprolite. When weathering proceeds, limonite

is formed rather than saprolite. Limonite has a higher content of Fe and a lower content of Ni

than saprolite.

[0003] Non Patent Literature 1 describes, as a method for using nickel oxide ore, a method for

producing ferronickel to be used as a raw material of stainless steel by subjecting saprolite to a

dry refining method, a method for recovering nickel from limonite by a wet refining method such

as high pressure acid leach (HPAL), and the like.

Citation List

Non Patent Literature

[0004] Non Patent Literature 1: Metal Resources Report, "Latest ore dressing technique

situation typical process by ore type (2) -Nickel-", by lichi Nakamura, Japan Oil, Gas and Metals

National Corporation (JOGMEC), July 31, 2013

Summary of Invention

Technical Problem

[0005] Recently, it is required to use not only saprolite having a high content of Ni but also

limonite having a low content of Ni. However, in the related art, a wet refining method such as

HPAL has been mainly used for a method for treating limonite having a low content of an iron

component. Even in a case where limonite is treated by a dry refining method like saprolite,

there are problems in that limonite cannot be treated, or a concentration of Ni in a ferronickel

product is not increased, and a range of use as a stainless steel raw material is limited to SUS200

or the like. In a case where a facility for treating both limonite and saprolite is designed, a cost

required for performing both wet refining of limonite and dry refining of saprolite is high.

Therefore, currently, saprolite having a high content of nickel (for example, a content of

nickel is 1.8 wt% or higher) is used in production of ferronickel, and saprolite having a lower

content of nickel than the saprolite (for example, a content of nickel is about 1.6 wt% or about 1.3

wt%) is used in production of nickel pig iron (NPI) having a low concentration of nickel by the

same method as in the ferronickel production. On the other hand, limonite having a low content

of an iron component and a content of nickel of about 1.2 wt% is subjected to an HPAL treatment,

and limonite having a high content of an iron component is used for producing NPI having a low

concentration of nickel (a content of nickel is 8 wt% to 3 wt%) in a blast furnace.

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

oxide ore capable of treating various types of nickel oxide ore such as limonite and saprolite by a

dry refining method regardless of a content of nickel.

Solution to Problem

[0007] A first aspect of the present invention is a method for processing nickel oxide ore, the

method including: an oxidizing roasting step of roasting a nickel oxide ore in an atmosphere

containing oxygen; and a sulfation roasting step of heating and roasting a roasted product obtained in the oxidizing roasting step 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, to produce a nickel sulfate compound.

[0008] A second aspect of the present invention is the method for processing nickel oxide ore

according to the first aspect, in which in the oxidizing roasting step, FeOOH contained in the

nickel oxide ore is converted into Fe 2 03 or Fe304.

[0009] A third aspect of the present invention is the method for processing nickel oxide ore

according to the first or second aspect, in which a roasting temperature in the sulfation roasting

step is 600°C to 700°C.

[0010] A fourth aspect of the present invention is the method for processing nickel oxide ore

according to any one of the first to third aspects, in which a roasting furnace used in the oxidizing

roasting step is a rotary kiln, and the rotary kiln is combined with an electric furnace for use in a

step of refining ferronickel from the nickel oxide ore.

[0011] A fifth aspect of the present invention is the method for processing nickel oxide ore

according to any one of the first to fourth aspects, in which the nickel oxide ore contains limonite

or saprolite.

[0012] A sixth aspect of the present invention is a device for processing nickel oxide ore, the

device including: an oxidizing roasting furnace for roasting a nickel oxide ore in an atmosphere

containing oxygen; and a sulfation roasting furnace for heating and roasting a roasted product

obtained in the oxidizing roasting furnace 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, to produce a nickel sulfate compound.

Advantageous Effects of Invention

[0013] According to the first aspect, even in a case where nickel oxide ore contains an iron

component, a nickel component is converted into a nickel sulfate compound, and conversion from

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

of a sulfur component by the iron component and to improve production efficiency of the nickel

sulfate compound.

[0014] According to the second aspect, the iron component contained in the nickel oxide ore is

prevented from being reduced to FeO in the oxidizing roasting step, such that the heating

temperature is low, and consumption of a reducing agent is low. Therefore, a cost such as energy

consumption can also be reduced as compared to an operation condition of a calcination furnace

used in production of ferronickel.

[0015] According to the third aspect, 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. Even in a case where the nickel

oxide ore contains manganese, the manganese forms a spinel structure with iron, and thus, the

manganese can be easily removed as an insoluble matter.

[0016] According to the fourth aspect, even in a case where the operation is performed in an

area where nickel oxide ore is produced, a facility for producing a nickel sulfate compound or a

facility for producing ferronickel can be used depending on a content of nickel in ore, a demand

and price of a product, and the like. The nickel sulfate compound is produced by a dry refining

method, such that the rotary kiln can be used for both production of the nickel sulfate compound

and production of ferronickel, thereby reducing an investment cost for a facility.

[0017] According to the fifth aspect, since nickel oxide ore, which is relatively easily available,

can be used, productivity can be increased.

[0018] According to the sixth aspect, even in a case where nickel oxide ore contains an iron component, a nickel component is converted into a nickel sulfate compound, and conversion from the iron component into iron sulfate is suppressed. Thus, it is possible to suppress consumption of a sulfur component by the iron component and to improve production efficiency of the nickel sulfate compound.

Brief Description of Drawings

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

processing nickel oxide ore according to an embodiment.

FIG. 2 is a schematic view illustrating an example of a roasting device.

FIG. 3 is a view illustrating a conceptual phase diagram of each of a Ni-S-O system and

an Fe-S-O system.

FIG. 4 is a configuration view illustrating a device used in Examples.

Description of Embodiments

[0020] Hereinafter, the present invention will be described based on preferred embodiments.

[0021] FIG. 1 is a configuration view schematically illustrating a method and device for

processing nickel oxide ore according to the present embodiment. In a treatment method of the

present embodiment, for example, in a case where nickel sulfate compounds 32 and 42 are

produced from nickel oxide ore 12, a first heating step 10 performed using afirst heating furnace

11 is an oxidizing roasting step. In addition, in a case where ferronickel 52 is produced from the

nickel oxide ore 12, the first heating step 10 performed using the first heating furnace 11 is a

calcining step.

[0022] In a case where a nickel sulfate compound is produced from nickel oxide ore, a roasted

product 13 obtained by oxidizing roasting of the nickel oxide ore is fed to a sulfation roasting step

20 (second heating step) performed using a second heating furnace 21. In the sulfation roasting

step 20, a nickel component contained in the roasted product 13 derived from the nickel oxide ore

12 is converted into a nickel sulfate compound by sulfation roasting. A sulfur source 23 may be

added in the sulfation roasting step 20. A roasted product 22 produced in the sulfation roasting

step 20 is separated into a solution containing the nickel sulfate compound 32 and an insoluble

matter 33 such as iron oxide, by adding water 34 in a water dissolution step 30 (water dissolution

means 31) and then performing solid-liquid separation. After the water dissolution step 30, the

nickel sulfate compound 42 from which impurities 43 are removed can be obtained by a

purification step 40 (purification means 41).

In a case where ferronickel is produced from nickel oxide ore, a calcined product 14

obtained by calcination of the nickel oxide ore can be fed to a refining furnace such as an electric

furnace 51, and a refining step 50 can be performed.

[0023] In a case where a nickel sulfate compound is produced from nickel oxide ore, roasting

furnaces (roasting devices) used in the oxidizing roasting step and the sulfation roasting step may

be different from each other. In addition, for example, as illustrated in FIG. 2, a roasting device

60 including a roasting furnace 61 provided by connecting a partition 61A for performing the

oxidizing roasting step and apartition 61B forperformingthe sulfation roasting step maybeused.

An example of the roasting furnace 61 can include a rotary kiln. The roasting furnace 61 has an

inlet 62 through which the nickel oxide ore is fed, a sulfur source feed part 63 arranged in the

middle of the roasting furnace 61, and an outlet 64 through which the roasted product is discharged.

The oxidizing roasting step is performed between the inlet 62 and the sulfur source feed part 63,

and the sulfation roasting step is performed between the sulfur source feed part 63 and the outlet

64, such that it is possible to obtain a roasted product containing a nickel sulfate compound.

[0024] 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%). It is possible to add a raw material substance containing a nickel component such as

nickel oxide or nickel hydroxide to the nickel oxide ore to be fed to the roasting furnace.

[0025] It is preferable to reduce a particle size of each of the nickel oxide ore and the additional

raw material by operations such as shredding, crushing, and grinding, prior to the oxidizing

roasting step. Since a reaction is initiated from a surface of the raw material in the roasting step,

the smaller the particle size of the raw material, the shorter the reaction time, which is preferable.

A crushing means 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. A particle size after crushing

is not particularly limited. In a case of a raw material available in a form of fine particles, such

as limonite ore, the raw material may be fed to the oxidizing roasting step as it is. When the raw

ore is fed to the oxidizing roasting step, the raw ore may be dry powder or may be in a form of

slurry containing water. In a case where the raw ore is subjected to primary drying, the device is

not particularly limited. A device that performs crushing and drying as a series of operations,

such as a jaw crusher, may be used, or a drying device such as a rotary dryer or an impact dryer

can be used. Since the limonite ore contains a large amount of fine powder, in a case where the

limonite ore is used, it is preferable to add an operation for recovering dust to the roasting furnace.

[0026] The oxidizing roasting step is, for example, a step of roasting the nickel oxide ore in an

oxidizing atmosphere containing oxygen (02) such as air. In order to maintain the iron

component in a form of iron oxide in a sulfation roasting step described below, it is preferable that

FeOOH contained in the nickel oxide ore is converted into Fe203 or Fe304 in the oxidizing roasting

step. A roasting temperature (oxidizing roasting temperature) in the oxidizing roasting step may

be, for example, 700°C or lower, and as a specific example, may be 500°C, 550°C, 600°C, 650°C,

700°C, or a temperature in a range of lower or higher than these temperatures or in the middle of

these temperatures. The oxidizing roasting temperature is a temperature at which FeOOH, Fe203,

or Fe304 is not easily thermally decomposed into FeO, and is preferably a temperature lower than

a calcining temperature.

In a case where the nickel oxide ore is refined to ferronickel, a heating temperature in

the calcining step is a temperature at which FeOOH, Fe 2 0 3 , or Fe304 is easily converted into FeO,

and may be, for example, 800 to 1,100°C. Iron oxide in the ore is converted into FeO, such that

it is easy to extract FeO-SiO2 slag when performing the step of refining ferronickel from the

calcined product in the electric furnace or the like.

[0027] Since an oxidizing roasting furnace can also be used as a calcination furnace in a

ferronickel refining facility according to the related art, a facility required for sulfation roasting

and a dissolution and purification device can be further added, and the treatment method of the

present embodiment can also be performed. In an area where nickel oxide ore is obtained,

ferronickel and a nickel sulfate compound can be selectively produced.

For example, in a case where saprolite having a high content of Ni is used as a raw

material, ferronickel may be produced from saprolite. The content of Ni contained in the

saprolite used for production of ferronickel is preferably 1.8 wt% or higher on a dry basis

excluding water. The content of Ni in the saprolite may be, for example, 1.8 wt%, 2.0 wt%, 2.5

wt%, 3.0 wt%, or the like, but is not limited thereto. In case where saprolite or limonite having

a low content of Ni (for example, a content of Ni is lower than 1.8 wt%) is used as a raw material,

a nickel sulfate compound may be produced through sulfation roasting. In saprolite or limonite

having a low content of Ni, a content of Ni may be, for example, 1.6 wt%, 1.5 wt%, 1.3 wt%, 1.0

wt%, or the like, but is not limited thereto. For determining which one of ferronickel or a nickel

sulfate compound is to be produced, in addition to the content of Ni in the nickel oxide ore, a

demand, a price, a production cost, and the like of the ferronickel or the nickel sulfate compound,

which is a product, may be considered. A nickel sulfate compound can be produced from the

saprolite having a high content of Ni.

In a case where the calcination furnace is operated as an oxidizing roasting furnace, as

described above, the heating temperature is lowered and consumption of a reducing agent is

reduced so as to suppress production of FeO. Therefore, a cost such as energy consumption can be reduced as compared to an operation condition of the calcination furnace.

[0028] The sulfation roasting step is a step of sulfation roasting the roasted product obtained in

the oxidizing roasting step to produce a nickel sulfate compound. As illustrated in FIG. 3, the

sulfation roasting step is 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-0 system and iron oxide is more thermodynamically stable than iron sulfate in an Fe-S

0 system.

[0029] FIG. 3 is a view illustrating an example of a conceptual phase diagram of each of the

Ni-S-0 system and the Fe-S-0 system. Boundary lines between phases in the Ni-S-0 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. 3, 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. 3, 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).

[0030] An example of the nickel sulfate contained in the Ni-S-0 system can include NiSO 4 ,

and an example of the nickel oxide contained in the Ni-S-0 system can include NiO. Inthephase

diagram illustrated in FIG. 3, 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

stablephase. 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.

[0031] Examples of the iron sulfate contained in the Fe-S-0 system can include FeSO 4 and

Fe2(SO 4 )3, and an example of the iron oxide contained in the Fe-S-0 system can include Fe 2 0 3

. In the phase diagram illustrated in FIG. 3, 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 SO 2 partial pressure and the 02 partial

pressure are higher than the boundary line LFe, the iron sulfate becomes a thermodynamically

stablephase. 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.

[0032] According to the phase diagram illustrated in FIG. 3, 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.

[0033] A roasting temperature (sulfation roasting temperature) in the sulfation roasting step is

preferably 400 to 750°C, and more preferably 550 to 750°C. Asa specific example, the sulfation

roasting temperature may be 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 sulfation roasting temperature is more preferably 600 to 700°C. At the above

temperature, even in a case where an object to be sulfated roasted, that is, an oxidized roasted

product, contains manganese (Mn) as an impurity derived from a raw material such as nickel oxide

ore, the manganese forms a spinel structure with iron, and thus, the manganese can be easily

removed as an insoluble matter.

[0034] As for the 02 partial pressure in the sulfation 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. 3. Therefore, production of nickel sulfate

can be accelerated while suppressing production of iron sulfate. The optimum region deviates

slightly depending on the sulfation 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)).

[0035] As for the S02 partial pressure in the sulfation 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 -1 to 0. Even in the

overlapping region A of FIG. 3, 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 sulfation roasting

step does not become excessively high, and thus, the facility can be easily handled.

[0036] The roasting device with which the sulfation roasting step is performed is not

particularly limited, and examples thereof can include a rotary kiln, a fluidized bed type heating furnace, a shelf-type roasting furnace, a multi-stage roasting furnace, and various other roasting furnaces. In order to maintain the condition in which the 02 partial pressure is low in the roasting device, an inert gas such as nitrogen (N2 ) or argon (Ar) may be fed to the roasting device. The inert gas can be used as a carrier when feeding a volatile component such as gas or steam to the roasting device. In a case where the amount of the sulfur component contained in a raw material such as nickel oxide ore is small, the sulfur component may be fed in the sulfation roasting step.

A feedstock of a sulfur component (sulfur source) is not particularly limited, and examples thereof

can include solid sulfur (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 elemental sulfur, it is preferable to generate S02 gas in an oxygen-enriched state.

[0037] A roasted product containing a nickel sulfate compound is obtained through the sulfation

roasting step. A solution containing the nickel sulfate compound is obtained through a water

dissolution step of dissolving the nickel sulfate compound in water by feeding water to the roasted

product. As described above, since the iron component contained in the roasted product in the

sulfation roasting step becomes a form which is sparingly soluble in water, such as iron oxide or

iron sulfide, the solution containing the nickel sulfate compound is separated into a solid phase

and a liquid phase by solid-liquid separation, such that a nickel sulfate compound is obtained as a

liquid phase, and impurities containing the iron component and the like are separated as a solid

phase. Further, if necessary, for example, a purification step 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.

[0038] In the water dissolution step, water added to the roasted product is preferably pure water

that is treated so as not to contain impurities. The water treatment method is not limited but may

be, for example, one or more selected from filtration, membrane separation, ion exchange,

distillation, sterilization, 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.

[0039] Solubility of nickel sulfate in water is highest at 150°C, at which 55 g of NiSO 4 is

contained in 100 g of the solution, but 22 g of NiSO 4 is contained 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 solution 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 solution is maintained in a heated state at a concentration

of NiSO 4 higher than the concentration.

[0040] 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. It is preferable to use a device having a high performance

for separation of fine particles contained in the solid phase. 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.

[0041] 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, Fe2 0 3 , and Fe 30 4, and thus, the impurities are easily removed from the nickel sulfate compound. In the sulfation 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 a nickel sulfate compound having a small amount of an iron component. A residue containing iron oxide and the like after the nickel sulfate compound is dissolved can be reused as an iron component for cement. In addition, the residue containing a large amount of an iron component such as iron oxide 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 nickel oxide ore 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.

[0042] 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 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.

[0043] The solution obtained through the water dissolution and solid-liquid separation contains

the nickel sulfate compound as a main component. Therefore, the solution of the nickel sulfate

compound can be transported and used 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 solution, for

example, cobalt sulfate or the like, depending on use, techniques such as solvent extraction, electrodialysis, electrowinning, electro refining, ion exchange, and crystallization can be used.

[0044] 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.

[0045] 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

insolvent, or addition of other substances. In this case, purification maybe 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.

[0046] 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.

[0047] According to the method and device for processing nickel oxide ore of the present

embodiment, the following effects can be obtained.

(1) By combining oxidizing roasting and sulfation roasting, a high-purity nickel sulfate

compound can be produced from nickel oxide ore.

(2) The roasting furnace can also be used as a calcination furnace in the step of producing

ferronickel from the nickel oxide ore by dry refining.

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

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

(4) Since the 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.

(5) A facility cost can be reduced as compared to the method according to the related art,

and the existing facility can be used as the roasting furnace.

[0048] 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.

For example, when designing a facility, an arrangement design for a general facility for

producing ferronickel is carried out, and an additional design can be added so that the roasted

product is transferred from the outlet of the calcination furnace to the sulfation roasting furnace.

For example, in a case where it is required to produce only the nickel sulfate compound,

installation of an electric furnace for producing ferronickel may be omitted. On the contrary, in

a case where a demand for ferronickel is high, firstly, installation of an electric furnace or start of

production of ferronickel may be carried out, and then installation of a sulfation roasting furnace

or start of production of a nickel sulfate compound may be carried out. As such, even in a case

where a market and demand for a nickel product is uncertain, since both a facility for producing

nickel sulfate using limonite oxide ore and a facility for producing ferronickel using saprolite

oxide ore can perform the treatment by a dry method, it is possible to operate an integrated

treatment in the same area where nickel oxide ore is produced, and it is also advantageous from

the viewpoint of avoiding an investment risk.

Examples

[0049] (1) Nickel oxide ore

Nickel limonite ore from Surigao Island, Philippines was used in a test described below.

Analysis results of a mineral composition (wt%) are as follows.

[0050] Fe component: 41%, MgO: 16%, SiO 2 : 3%, A1 2 0 3 : 2.7%, Cr component: 0.15%, Ni

component: 1.2%, Co component: 0.05%, other solid contents: 5.9%, water: 30%

[0051] Goethite (FeOOH) accounted for 55% of the Fe component (41% in ore). MgO(16%

in ore) was mainly montmorillonite (CaMg2Si 4 1o(OH)2). SiO 2 (3% in ore) was mainly the

montmorillonite and serpentine ((Mg,Fe)3Si2O 5 (OH) 4). The Ni component (1.2% in ore), the Co

component (0.05% in ore), and the like were contained in a sample ore, and water accounted for

30% of the sample ore.

[0052] (2) Test device used in roasting test

A test device 100 illustrated in FIG. 4 was used in the roasting test. Asampleofnickel

oxide ore is placed on a saucer 101. The saucer 101 is set inside a glass container 102 installed

in an electric furnace 103. The glass container 102 is provided with a thermometer 104, such as

a thermocouple, that can measure an atmospheric temperature, an injection pipe 105 through

which various types of gas can be injected, and an outlet 106 for an exhaust gas generated inside.

The electric furnace 103 can heat the sample by raising the temperature to a desired temperature.

SO 2 gas containing dry air or nitrogen gas can be fed to the injection pipe 105, if necessary, while

constantly injecting argon gas. The exhaust gas discharged from the outlet 106 can pass through

a gas analyzer 107 and then can be treated by an exhaust gas treatment device 108. Various data

of gas amounts and analytical values can be collected on a computer (not illustrated).

[0053] (3) Oxidizing roasting step

10 g of nickel limonite ore was collected in a container, and the ore was dried at110°C

for 2 hours to remove water. 5 g of the dried ore was weighed on the saucer 101. The glass

container 102 was set in the electric furnace 103, and the saucer 101 with the weighed ore was set

in the glass container 102. The glass container 102 was provided with the thermometer 104

having a thermocouple that can measure an atmospheric temperature, the injection pipe 105 into

which various type of gas can be injected, and the outlet 106 for the generated exhaust gas, and

the sample was oxidized roasted by raising the temperature to a predetermined temperature in the

electric furnace 103. The oxidizing roasting temperature was 600°C and 700°C. During

oxidizing roasting, Ar or air was appropriately fed to the sample through the injection pipe 105

(S02 was not fed).

[0054] (4) Sulfation roasting step

The sulfation roasting step was performed under the following three conditions

following (3) Oxidizing roasting step.

(Condition Example 1) 50% of concentrated sulfuric acid was added to the sample to

perform adjustment at 600°C so that log p(O2) was -4 and logp(S02) was +1 to -1.

(Condition Example 2) Sulfur was added to the sample, oxygen was added in an amount

slightly insufficient for reaction to perform adjustment at 600°C so that log p(O2) was -4 and log

p(SO2) was +1 to -1.

(Condition Example 3) Sulfur was added to the sample, oxygen was added in an amount

slightly insufficient for reaction to perform adjustment at 700°C so that log p(O2) was -4 and log

p(SO2) was +1 to -1.

[0055] (5) Water dissolution step

Each of the three types of samples subjected to (3) Oxidizing roasting step and (4)

Sulfation roasting step was stirred with 50 g of pure water for 1 hour. A solid content in slurry

after stirring was filtered with a Millipore filtration separator. A filtrate passed through the

Millipore was subjected to atomic absorption spectrometry to measure a concentration of each of

nickel (Ni), iron (Fe), and manganese (Mn). From these measurement results, a proportion

(dissolution rate) of each of Ni, Fe, and Mn dissolved in pure water was determined based on 100

wt% of the amount of Ni, Fe, and Mn contained in the sample used in roasting. For example, the

dissolution rate of Ni refers to the proportion of Ni dissolved in pure water of Ni contained in the

roasted product. The results of calculating the dissolution rate (wt%) are shown below. The

number of each Condition Example corresponds to each Condition Example shown in (4)

Sulfation roasting step described above.

[0056] (Condition Example 1) Dissolution rate of Ni: 89%, dissolution rate of Fe: 1%,

dissolution rate of Mn: 75 %

(Condition Example 2) Dissolution rate of Ni: 86%, dissolution rate of Fe: 1%,

dissolution rate of Mn: 74%

(Condition Example 3) Dissolution rate of Ni: 86%, dissolution rate of Fe: 1%,

dissolution rate of Mn: 2%

[0057] From the calculation results of the dissolution rate, it was found that when sulfation

roasting was performed at 600°C or higher (in particular, at a temperature higher than 600°C), in

a reaction of Fe 2 03 + MnO -- MnFe204, Mn was difficult to be dissolved in water due to a spinel

structure formed by manganese and iron. Since it is known that the sulfate is decomposed when

the sulfation roasting temperature was 700°C or higher (in particular, a temperature higher than

700°C), it is considered that the sulfation roasting temperature is desirably 600°C to 700°C.

Industrial Applicability

[0058] 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

[0059] 10 First heating step (oxidizing roasting step or calcining step)

12 Nickel oxide ore

20 Sulfation roasting step

30 Water dissolution step

32 Nickel sulfate compound

40 Purification step

42 Purified nickel sulfate compound

50 Refining step

51 Electric furnace

52 Ferronickel

Roasting device

61 Roasting furnace

61A Partition for performing oxidizing roasting step

61B Partition for performing sulfation roasting step

Claims (6)

1. A method for processing nickel oxide ore, the method comprising:

an oxidizing roasting step of roasting a nickel oxide ore in an atmosphere containing

oxygen;and

a sulfation roasting step of heating and roasting a roasted product obtained in the

oxidizing roasting step 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, to

produce a nickel sulfate compound.

2. The method for processing nickel oxide ore according to claim 1, wherein

in the oxidizing roasting step, FeOOH contained in the nickel oxide ore is converted

into Fe 2 03 or Fe 3 0 4 .

3. The method for processing nickel oxide ore according to claim 1 or 2, wherein

a roasting temperature in the sulfation roasting step is 600°C to 700°C.

4. The method for processing nickel oxide ore according to any one of claims 1 to 3,

wherein

a roasting furnace used in the oxidizing roasting step is a rotary kiln, and

the rotary kiln is combined with an electric furnace for use in a step of refining

ferronickel from the nickel oxide ore.

5. The method for processing nickel oxide ore according to any one of claims 1 to 4,

wherein the nickel oxide ore contains limonite or saprolite.

6. A device for processing nickel oxide ore, the device comprising:

an oxidizing roasting furnace for roasting a nickel oxide ore in an atmosphere containing

oxygen;and

a sulfation roasting furnace for heating and roasting a roasted product obtained in the

oxidizing roasting furnace 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, to produce a nickel sulfate compound.