AU2018256247A1 - Method for smelting ilmenite using red mud - Google Patents

Method for smelting ilmenite using red mud Download PDF

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Publication number
AU2018256247A1
AU2018256247A1 AU2018256247A AU2018256247A AU2018256247A1 AU 2018256247 A1 AU2018256247 A1 AU 2018256247A1 AU 2018256247 A AU2018256247 A AU 2018256247A AU 2018256247 A AU2018256247 A AU 2018256247A AU 2018256247 A1 AU2018256247 A1 AU 2018256247A1
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Australia
Prior art keywords
titanium dioxide
red mud
mixture
iron
ilmenite
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AU2018256247A
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AU2018256247B2 (en
Inventor
Kyeong-Woo Chung
Min-Cheol Ha
Ho-Seok Jeon
Min-Seuk Kim
Young-Jae Kim
Hyun-Sik Park
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Korea Institute of Geoscience and Mineral Resources KIGAM
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Korea Institute of Geoscience and Mineral Resources KIGAM
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Priority claimed from KR1020170050662A external-priority patent/KR101790128B1/en
Priority claimed from KR1020180041532A external-priority patent/KR101900672B1/en
Application filed by Korea Institute of Geoscience and Mineral Resources KIGAM filed Critical Korea Institute of Geoscience and Mineral Resources KIGAM
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C1/00—Magnetic separation
    • B03C1/02—Magnetic separation acting directly on the substance being separated
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G23/00—Compounds of titanium
    • C01G23/04—Oxides; Hydroxides
    • C01G23/047—Titanium dioxide

Abstract

The present invention provides a method for smelting ilmenite using red mud, the method comprising the steps of: mixing an ilmenite concentrate and red mud to form a mixture; adding a carbon source to the mixture, followed by heating to reduce iron in the mixture to form a molten droplet; subjecting the molten droplet to magnetic separation to remove the iron and recover a titanium dioxide slag; introducing the titanium dioxide slag into a Bayer process to recover alumina (Al

Description

METHOD FOR SMELTING ILMENITE USING RED MUD [Technical Field]
The present disclosure is related to a method of smelting ilmenite which is an ore for titanium, particularly to a method of smelting ilmenite whereby a high quality of titanium dioxide can be obtained and process byproducts can be recovered and utilized.
[Background Art]
The titanium raw material industry producing titanium is dominated by ilmenite produced from heavy sand ore deposits in Australia, South Africa, India regions or from hard rock ore deposits in Canada and Norway. Australia is the world's largest producer of heavy ore concentrates and more than half of ilmenite is produced as synthetic rutile and used as pigment raw material.
Ilmenite can be used directly in the production of titanium dioxide pigments, but most of ilmenite is improved in its quality by producing a titanium dioxide slag or synthetic rutile.
Another important raw material is natural rutile, which is produced as a by-product of ilmenite in Australia, the United States and South Africa and as the main mineral in Sierra Leone.
Ilmenite (FeO-TiCh) has a content of generally 45 to 65% by weight of TiCh. Due to advances in chemical and dry smelting technology, it is possible to remove iron component to improve the T1O2 content in synthetic rutile up to 90 ~ 96%.
As a commercial process for preparing artificial rutile from ilmenite, there is the Becher process.
In the Becher process, artificial rutile is prepared through a two-step process of reduction and aeration.
In the first step, ilmenite is coated with iron using sub-bituminous coal as fuel and reducing agent at a high temperature of 1300 °C. The reaction proceeds according to Reaction Scheme 1 below.
[Reaction Scheme 1]
Fe2O3-TiO2 + 3CO (2Fe + T1O2) + 3CO2
The iron component is oxidized by blowing air in an ammonium chloride solution at a temperature up to 80 °C (aeration).
Using a hydrocyclone, artificial rutile (T1O2, 90%) with a standard quality is separated from hydrous iron oxide concentrated and pumped to a reservoir, and the general reaction is performed according to Reaction Scheme 2 below.
[Reaction Scheme 2] (2Fe + T1O2) + O2 2FeO + T1O2
At this time, when reducing at 1300 °C in the course of using iron, it is impossible to physically separate the reduced iron. Therefore, iron is again oxidized to an oxide in the subsequent aeration process and then subjected to acid-leaching, thereby separating and recovering iron and improving the quality of titanium dioxide.
According to the conventional Becher process, since the reduced iron produced in the reduction process cannot be separated in advance and the purity of titanium dioxide is increased afterwards through the aeration and acid leaching processes, the load of the aeration and acid leaching processes is greatly increased.
Meanwhile, red mud is a workplace waste generated from a bauxite refining process and consists of a strong alkaline material with a water content of 40-55% and a pH of 11-13.
In addition, although hydrous aluminum silicate and quartz are contained in a large amount, a utilization method thereof has not been disclosed yet. Since red mud is strongly oxidative and thus difficult to treat, the development of new utilization methods is desperately needed.
As prior literatures related thereto, Korea Laid-Open Patent Publication No. 10-2017-0021759 (Publication date: 2017.02.28) discloses a fabrication method of metal titanium using an ilmenite ore.
[Detailed Description of the Invention] [Technical Problem]
Therefore, the present disclosure is related to a method of smelting ilmenite using red mud, and provides a method of smelting ilmenite using red mud which is waste difficult to utilize, since red mud which was conventionally difficult to utilize can be used as flux or raw material to smelt ilmenite and recover highly pure titanium dioxide.
It is possible to improve the efficiency of the process by increasing the quality of titanium dioxide recovered from the smelting process and simultaneously to provide a new utilization method of red mud by separating alumina (AI2O3) which has been included in the red mud added as flux.
The problem to be solved by the present disclosure is not limited to the problem(s) mentioned above, and other object (s) not mentioned will be clearly understood by those skilled in the art from the following description.
[Technical Solution]
In order to solve the above problems, the present disclosure is directed to provide a method for smelting ilmenite using red mud, including a step of mixing an ilmenite concentrate and red mud to form a mixture, a step of adding a carbon source to the mixture, followed by heating to reduce iron in the mixture, a step of separating the reduced iron through magnetic separation; and a step of subjecting residue to aeration and acid-leaching to remove iron in the residue and recover titanium dioxide.
In order to solve the above problems, the present disclosure is also directed to provide a method for smelting ilmenite using red mud, including (a) a step of mixing an ilmenite concentrate and red mud to form a mixture; (b) a step of adding a carbon source to the mixture, followed by heating to reduce iron in the mixture to form molten droplets; (c) a step of physically separating the molten droplets to remove the iron and recover a titanium dioxide slag; (d) a step of introducing the titanium dioxide slag into a Bayer process to recover alumina (AI2O3) ; and (e) a step of subjecting the aluminaseparated titanium dioxide slag to acid-leaching to remove silica (SiO2) · [Advantageous Effects]
According to the present disclosure, red mud which is generated from the process of smelting aluminum oxide and difficult to treat can be treated together in the process of smelting ilmenite by using as flux or raw material.
Also, when red mud and ilmenite concentrate are mixed and heated to be reduced, iron and titanium dioxide contained in ilmenite as well as iron and titanium dioxide contained in red mud can be separated and recovered all at once and thus the recovery efficiency of iron and titanium dioxide can be largely improved.
In addition, it is possible to largely improve the quality of titanium dioxide slag that remains after physically sorting and separating iron which is an impurity contained in ilmenite, not by reducing the iron at a high temperature, but by reducing with red mud to form molten droplets .
Also, it is possible to dramatically reduce the cost for the process of smelting ilmenite since an aeration step for recovering a high-quality titanium dioxide is not necessary, by minimizing iron content, an impurity in the titanium dioxide slag that is recovered by separating and recovering iron reduced through a reduction process wherein a carbon source is added to adjust a heating temperature and magnetic separation
Also, in the process of smelting titanium dioxide using ilmenite concentrate, it is possible to recover a highquality titanium dioxide and obtain an iron scrap as a byproduct by utilizing red mud which is a waste material that is very difficult to treat, and the alumina contained in red mud is recovered, thus it is very environmentally friendly.
[Description of the Drawings]
FIG. 1 is a process flow chart of the method of smelting ilmenite using red mud according to an embodiment of the present disclosure.
FIG. 2 is a process flow chart of the method of smelting ilmenite using red mud according to another embodiment of the present disclosure.
FIG. 3 is a photograph of ilmenite, red mud and freeburning coal samples which are starting materials in the method of smelting ilmenite using red mud according to an embodiment of the present disclosure.
FIG. 4 is a photograph showing molten droplets of iron reduced by heating in the method of smelting ilmenite using red mud according to an embodiment of the present disclosure .
FIG. 5 is a schematic diagram showing the configuration of the method of smelting ilmenite using red mud according to another embodiment of the present disclosure.
FIG. 6 is a photograph of a high temperature and high pressure leaching apparatus.
FIG. 7 is a graph showing alumina and silica contents depending on caustic soda concentration in the Bayer process step in the method of smelting ilmenite using red mud according to another embodiment of the present disclosure .
[Best Mode for carrying out the Disclosure]
FIG. 5 is a schematic diagram showing the configuration of the method of smelting ilmenite using red mud according to another embodiment of the present disclosure.
Referring to FIG. 5, a mixture of ilmenite concentrate 100 g and red mud 100 g was pressurized to prepare briquettes .
Powdered ilmenite concentrate and red mud were uniformly mixed through a ball mill and then briquetted using a pelletizer with a pressure of 5 tons at maximum.
A free-burning coal was added to the briquette, which was reduced by heating at 1700 °C for 15 minutes in a rotary furnace.
It was confirmed that a high-temperature melt occurred and the resulting molten droplets and residue were identified.
The molten droplets were separated using a magnetic separator .
The titanium dioxide slag was recovered by removing molten droplets.
FIG. 6 is a photograph of a high temperature and high pressure leaching apparatus.
Referring FIG. 6, in the high temperature and high pressure leaching apparatus was charged caustic soda together with titanium dioxide slag from which molten droplets were removed and a leaching was made under a condition of 200 °C and 20 bar for 1 hour.
After leaching, leached components were analyzed to determine the content of alumina and silica in the titanium dioxide slag.
An acid-leaching was performed by adding sulfuric acid at a concentration of 30% to titanium dioxide slag from which alumina was removed.
The quality of the finally-recovered titanium dioxide slag was determined.
[Mode for carrying out the Invention]
Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.
The advantages and features of the present disclosure and the manner of achieving them will be apparent by reference to various embodiments described in detail below with reference to the accompanying drawings.
However, the present disclosure is not limited to the embodiments described below, but may be embodied in various other forms, and these embodiments are provided in order to complete the disclosure of the present disclosure and to completely inform those of ordinary skill in the art of the scope of the present disclosure. The present disclosure is only defined by the appended claims.
Also, in the following description of the present disclosure, a detailed description of a configuration that is considered to unnecessarily obscure the gist of the present disclosure, for example, a known technology including the prior art, may be omitted.
FIG. 1 is a process flow chart of the method of smelting ilmenite using red mud according to an embodiment of the present disclosure.
Referring FIG. 1, the method for smelting ilmenite using red mud according to another embodiment of the present disclosure includes mixing an ilmenite concentrate and red mud to form a mixture in step S100, adding a carbon source to the mixture, followed by heating to reduce iron in the mixture in step S200, separating the reduced iron through a magnetic separation in step S300 and subjecting the residue to aeration and acid-leaching to remove iron in the residue and recover titanium dioxide in step S400.
The ilmenite concentrate may be those that the quality is improved by beneficiation of ilmenite ore.
The ilmenite concentrate may contain titanium dioxide (TiO2) in 17 to 50 % by weight.
The quality of ilmenite concentrate is qenerally 45 % to 50 %, but the hiqher the quality of titanium is, the higher the process cost is.
In addition, since domestic ilmenites generally have a low quality of 17% to 50%, it is very difficult to use them for smeltinq titanium dioxide, but when a low-quality ilmenite concentrate and red mud are mixed and smelted, a hiqh-quality titanium dioxide can be obtained.
The ilmenite concentrate may contain titanium dioxide and remained iron oxide (FeOx) in 35 to 65 % by weight.
The iron oxide is reduced and recovered by separating at the step of a magnetic separation
The red mud may be a waste generated from a smelting process of aluminum oxide.
The red mud has a high pH and thus difficult to dispose of as itself, but when mixed with ilmenite concentrate and then reduced, iron and titanium dioxide contained in red mud may be separately recovered.
The red mud can contain titanium dioxide (TiO2) at 5 to % by weight.
Titanium dioxide contained in the red mud may be recovered together with titanium dioxide contained in ilmenite concentrate.
The red mud may contain remaining hematite (Fe2O3) at 30 to 40 % by weight in addition to titanium dioxide.
Iron oxide contained in red mud may be hematite.
The hematite in red mud may be reduced together with iron oxide component of ilmenite concentrate and can be physically separated.
The red mud may be added in an amount of 10 to 200 parts by weight based on 100 parts by weight of the total amount of ilmenite concentrate.
Iron oxide contained in the red mud has a very fast reduction rate compared to ilmenite and thus firstly changes to reduced iron.
The resulting reduced iron is carburized by carbon and has a low melting point and acts as a strong reducing agent by itself to facilitate the reduction of ilmenite and to
greatly increase the production of molten droplets of
reduced iron .
When the red mud is added in less than 10 parts by
weight, the purity of titanium dioxide separated and
recovered becomes low, and when it exceeds 200 parts by weight, there may be a problem that the efficiency of the process of reducing iron by heating becomes greatly low.
In the step of forming a mixture by mixing ilmenite concentrate and red mud, the mixture may be pressed to form a briquette (pellet).
In the case of forming the mixture into briquettes, the efficiency of the subsequent heating and reducing step may be greatly improved, and the convenience of process operation may be greatly increased in a reduction process using a rotary furnace or a sintering furnace.
The carbon source may be any one selected from freeburning coals consisting of peat, brown coal and bituminous coal.
The carbon source may increase the reaction temperature in the step of heating and reducing the mixture, and the reduced iron reduced by carbon may become a very strong reducing agent to greatly improve the efficiency of the reduction step.
The carbon source may be added in 10 to 100 parts by weight based on total 100 parts by weight of the mixture.
When the carbon source is added in less than 10 parts by weight, it is difficult to increase the temperature to a temperature required for the reduction reaction, and when the carbon source exceeds 100 parts by weight, an extra amount of carbon source may be added to increase the process cost, thereby reducing the overall efficiency.
Here, when the carbon source is set to maximum within the above range, a maximum reduction rate may be expected, and there is an advantage in that any unreacted residual carbon can be recovered and reused.
The iron in the mixture can be reduced by adding a
carbon source to the mixture and heating to 1350 to 1500 °C
for 8 to 12 hours.
When heated below 1350 °C, the mixture of ilmenite
concentrate and red mud does not reach the melting
temperature and thus does not melt. When heated within the above range, it is possible to proceed the reduction roasting sufficiently, to control the composition of components such as alumina, silica, and the like in the produced slag, and to physically separate the reduced iron component.
The above heating can be performed at a sintering furnace or a rotary furnace.
When using a sintering furnace (sinter bed) or a rotary furnace (rotary kiln), it is possible to easily heat to a setting temperature by adding a carbon source, and it is very advantageous to adjust the reaction temperature and reaction time during progressing the reducing reaction by heating.
The above reduced iron can be formed in a molten droplet shape .
When ilmenite concentrate and red mud are mixed and heated, iron of the iron oxide component in ilmenite concentrate and the iron oxide contained in red mud is reduced and discharged, and at this time, discharged in a molten droplet shape. The reduced iron can be separated through a magnetic separation in step S300.
When the reduced iron is formed in a molten droplet shape, iron components are agglomerated and easily attracted to magnetism, and iron components in ilmenite concentrate and red mud can be together separated by one process through a magnetic separation.
When iron is separated in advance through a magnetic separation, the load to the aeration and acid-leaching described later will be largely decreased.
In addition, iron is separated and removed from the residue, the content of titanium dioxide issued from ilmenite concentrate and red mud is increased, and thus the quality of titanium dioxide to be recovered is very improved.
The above residue is titanium dioxide slag.
Thereafter, the residue is subjected to aeration and acid-leaching to recover titanium dioxide in the residue in step S400.
The aeration can be made by introducing air into the residue for 30 minutes to 30 hours.
In case of not reaching to the above range, it is difficult to remove iron component remaining in the residue.
The acid-leaching can remove iron in the residue by using from 0.05% to 30% of sulfuric acid and leaching for 5 minutes to 10 hours.
The concentration of sulfuric acid can vary depending on the nature of the residue and can be selected on the relation of inverse proportion to the leaching time.
In the acid-leaching step, all iron components in the residue can be removed.
In the above aeration and acid-leaching step, all the gangue component can be removed, the iron component in the residue and the quality of titanium dioxide to be removed is greatly improved.
The above titanium dioxide has a quality of 88% to 95%.
Therefore, it is possible to provide a new smelting method which can recover titanium dioxide with a high purity by using as raw materials ilmenite with a very low quality and red mud which is difficult to dispose of.
In the smelting method according to an embodiment of the present disclosure, therefore, iron oxide contained in red mud is firstly reduced under a carbon source, and the reduced iron is then carburized by the carbon source to have a low melting point and thereby acts as a strong reducing agent, which facilitates the reduction of ilmenite and promotes the production of reduced iron into molten droplets .
In addition, a high-quality titanium dioxide is recovered by effectively removing iron from the residue through aeration and acid-leaching.
FIG. 2 is a process flow diagram of the method of smelting ilmenite using red mud according to another example of the present disclosure.
Referring to FIG. 2, the method of smelting ilmenite using red mud according to another embodiment of the present disclosure includes mixing an ilmenite concentrate and red mud to form a mixture in step F100, adding a carbon source to the mixture, followed by heating to reduce iron in the mixture to form molten droplets in step F200, subjecting the molten droplets to a magnetic separation to remove the iron and recover a titanium dioxide slag in step F300, introducing the titanium dioxide slag into a Bayer process to recover alumina (AI2O3) in step F400, and subjecting the alumina-separated titanium dioxide slag to acid-leaching to remove silica (SiCt) in step F500.
First, an ilmenite concentrate and red mud are mixed to form a mixture in step F100.
The ilmenite concentrate may be any one of which quality is improved by beneficiation of ilmenite ore.
The ilmenite concentrate may contain titanium dioxide (TiO2) in 17 to 50 % by weight.
The quality of ilmenite concentrate is generally 45 % to 50 %, but the higher the quality of titanium is, the higher the process cost is.
In addition, since domestic ilmenite generally has a low quality of 17% to 50%, it is very difficult to use it for smelting titanium dioxide, but when a low-quality ilmenite concentrate and red mud are mixed and smelted, a highquality titanium dioxide can be obtained.
The ilmenite concentrate may contain titanium dioxide and remained iron oxide (FeOx) in 35 to 65 %.
The iron oxide is reduced and recovered by separating in
The red mud may be a waste generated from a process of smelting aluminum oxide.
a magnetic separation step.
Red mud inc ludes titanium dioxide (T1O2) , alumina (Al 2Ο3)
and silica (SiO2) .
Red mud is difficult to dispose as itself due to its
very high pH, but when mixed with ilmenite concentrate and
then reduced, iron and titanium dioxide contained in red
mud can be separated and recovered.
Red mud can contain titanium dioxide (T1O2) in 5 to 10 % by weight.
Titanium dioxide contained in red mud can be recovered together with titanium dioxide contained in ilmenite concentrate .
Red mud includes alumina and silica.
The alumina and silica can be contained in titanium dioxide slag generated from the reduction process. In this case, since the quality of titanium dioxide is decreased, a step to remove the alumina and silica is needed, and thus a high-quality titanium dioxide can be obtained.
Said red mud may contain residual hematite (Fe2O3) in 30 to 40 wt% in addition to titanium dioxide.
The hematite in the red mud is reduced together with the iron component of the ilmenite concentrate to form molten droplets and can be physically separated through a magnetic separation .
Iron oxide contained in the red mud has a very fast reduction rate compared to ilmenite and thus firstly changes to reduced iron.
The resulting reduced iron is carburized by carbon and has a low melting point and acts as a strong reducing agent by itself to facilitate the reduction of ilmenite and to increase the production of molten droplets which are reduced iron.
The red mud is added in an amount of 10 to 200 parts by weight based on 100 parts by weight of the total amount of ilmenite concentrate.
When the red mud is added in less than 10 parts by weight, the quality of titanium dioxide separated and recovered does not reach 97%, when it exceeds 200 parts by weight, a problem may occur that the efficiency of the process of reducing iron by heating becomes very low.
In the step of forming a mixture by mixing ilmenite concentrate and red mud, the mixture may be pressed to form briquettes (pellets).
In the case of forming the mixture into briquettes, the efficiency of the subsequent heating and reducing step may be greatly improved, and the convenience of process operation may be greatly increased in a reduction process using a rotary furnace or a sintering furnace.
A carbon source is added to the mixture, which is heated to reduce iron in the mixture to form molten droplets in step S200.
The carbon source may be any one selected from free18 burning coals consisting of peat, brown coal, bituminous coal and the like.
The carbon source has a high volatility.
The carbon source may increase the reaction temperature in the step of heating and reducing the mixture, and the reduced iron reduced by carbon may become a very strong reducing agent to greatly improve the efficiency of the reduction step.
The carbon source may be added in 10 to 100 parts by weight based on total 100 parts by weight of the mixture.
When the carbon source is set to maximum, a maximum reduction rate may be expected, and there is an advantage in that any unreacted residual carbon can be recovered and reused.
When the carbon source is added in less than 10 parts by weight, it is difficult to increase the temperature to a temperature required for the reduction reaction, and when the carbon source exceeds 100 parts by weight, an extra amount of carbon source may be added to increase the process cost, thereby reducing the overall efficiency.
The iron in the mixture can be reduced and roasted by adding a carbon source to the mixture and heating to 1400 to 2000 °C for 15 minutes to 10 hours.
When heated below 1400 °C, the mixture of ilmenite concentrate and red mud does not reach the melting temperature and does not melt, and when heating within the above range, it is possible to adjust the composition of components of alumina and silica in the produced slag, and to physically separate the reduced iron component.
The above heating can be performed in any one selected from the group consisting of a sintering furnace, a rotary furnace and an arc furnace.
When using a sintering furnace (sinter bed) or a rotary furnace (rotary kiln), it is possible to easily heat to a setting temperature by adding a carbon source, and it is very advantageous to adjust the reaction temperature and reaction time during progressing the reducing reaction by heating.
When the heating is carried out in an arc furnace, the temperature can rapidly increase to a reduction temperature of 2000 °C and the weight of the reduced iron increase to allow gravity separation.
The above reduced iron can be formed in a molten droplet shape .
When ilmenite concentrate and red mud are mixed and heated, iron of the iron oxide component in ilmenite concentrate and the iron oxide contained in red mud is reduced and discharged, and at this time, discharged in a molten droplet shape.
It is possible to separate iron components by a single process using ilmenite concentrate and red mud, and the reduced iron can be easily sorted by a physical method and its recycling is possible.
The molten droplets are physically separated to remove iron and recover titanium dioxide slag in step F300.
When the reduced iron is formed in a molten droplet shape, iron components are agglomerated and easily attracted to magnetism, and iron components in ilmenite concentrate and red mud can be together separated by one process through a magnetic separation.
The molten droplet is contained in 25 to 30% by weight in the reduced material.
The weight of the molten droplet can be increased through steps for heating and reducing.
Also, when reduced in an arc furnace, the weight of iron is increased to allow gravity separation.
In the titanium dioxide slag, iron is separated and removed and the content of titanium dioxide issued from ilmenite concentrate and red mud is increased, and thus the guality of titanium dioxide to be recovered is very improved.
The titanium dioxide slag is introduced into a Bayer process to recover alumina (AI2O3) in step F400.
The Bayer process refers to a process of discharging alumina as crystals by adding caustic soda and leaching under the condition of a high temperature and a high pressure .
The titanium dioxide slag may contain alumina and silica derived from red mud.
In case that the alumina and silica are not removed, the guality of the recovered titanium dioxide may be lowered.
In the Bayer process, caustic soda (NaOH) may be added to a titanium dioxide slag and alumina may be leached at
150 to 200 °C at a pressure of 15 to 20 bar.
It is possible to recover alumina by the above alkaline leaching with caustic soda at the above high temperature and high pressure range. In case of not reaching the above temperature and pressure range, the leaching efficiency of alumina is decreased.
The Beyer process can leach alumina by adding from 1.25 to 6.25 M of caustic soda (NaOH) to a titanium dioxide slag.
Within the above concentration range, alumina may be and precipitated, and silica contained in titanium dioxide slag may be dissolved and leached together.
In case that the caustic soda is less than 1.25 M, it is difficult to contain alumina to less than 3% by weight in the titanium dioxide slag recovered.
By adjusting the concentration of caustic soda to control the content of alumina and silica in the titanium dioxide slag, it is possible to recover titanium dioxide with a high quality.
Thereafter, the titanium dioxide slag in which alumina was separated is subjected to acid leaching to remove silica (SiCt) in step F500.
The acid-leaching can remove silica in the titanium dioxide slag by using from 0.05% to 30% of sulfuric acid and leaching for 5 minutes to 10 hours.
The concentration of sulfuric acid can vary depending on the nature of the residue and can be selected on the relation of inverse proportion to the leaching time.
In the acid-leaching step, all iron components in the residue can be removed, and simultaneously, silica remained in the titanium dioxide slag can also be removed together.
Through the above acid-leaching, all of the gangue component and impurities in the titanium dioxide slag can be removed, and the quality of the final product of titanium dioxide slag is greatly improved by removing the remaining iron and silica.
The titanium dioxide slag recovered may have a quality of 70% to 97%.
The above titanium dioxide slag is used as a highquality titanium dioxide raw material such as pigment or the like.
In the smelting method according to another embodiment of the present disclosure, therefore, alumina (AI2O3) contained in red mud is separated and reused as well as the quality of titanium dioxide remained can be greatly improve by removing alumina and silica together with iron impurities .
Hereinafter, preferred examples are provided to help understanding of the present disclosure, but the following examples are merely to illustrate the present disclosure, and the scope of the present disclosure is not limited to the following examples.
<Example 1> Recovery of titanium dioxide via aeration and acid leaching
A mixture of ilmenite concentrate 100 g and red mud 100 g was pressed to prepare briquettes.
Powdered ilmenite concentrate and red mud were uniformly mixed through a ball mill and then briquetted using a pelletizer with a pressure of 5 tons at maximum.
A bituminous coal was added to the briquettes, which were heated to 1450 °C in a rotary furnace.
It was confirmed that a high-temperature melt occurred and the resulting molten droplets and residues were identified.
The molten droplets were separated using a magnetic separator. The residue was subjected to aeration by introducing air and to acid leaching by introducing sulfuric acid with a concentration of 30%.
The quality of recovered titanium dioxide was determined.
<Example 2> Recovery of titanium dioxide according to Beyer process
FIG. 5 is a schematic diagram showing the configuration of the method of smelting ilmenite using red mud according to another embodiment of the present disclosure.
Referring to FIG. 5, a mixture of ilmenite concentrate 100 g and red mud 100 g was pressed to prepare briquettes.
Powdered ilmenite concentrate and red mud were uniformly mixed through a ball mill and then briquetted using a pelletizer with a pressure of 5 tons at maximum.
Bituminous coal was added to the briquettes, which were reduced by heating to 2000 °C for 15 minutes in an arc furnace .
It was confirmed that a high-temperature melt occurred and the resulting molten droplets and residues were identified.
The molten droplets were separated using a magnetic separator .
The molten droplets were removed to recover the titanium dioxide slag.
FIG. 6 is a photograph of a high temperature and high pressure leaching apparatus.
Referring FIG. 6, in the high temperature and high pressure leaching apparatus was charged caustic soda together with titanium dioxide slag from which molten droplets were removed and a leaching was made under a condition of 200 °C and 20 bar for 1 hour.
After leaching, leached components were analyzed to determine the content of alumina and silica in the titanium dioxide slag.
An acid-leaching was made by adding sulfuric acid at a concentration of 30% to titanium dioxide slag from which alumina was removed.
The quality of the finally-recovered titanium dioxide slag was determined.
<Experiment 1> Remove of iron by reduction
FIG. 3 is a photograph of ilmenite, red mud and freeburning coal samples which are starting materials in the method of smelting ilmenite using red mud according to an embodiment of the present disclosure.
FIG. 4 is a photograph showing molten droplets of iron reduced by heating in the method of smelting ilmenite using red mud according to an embodiment of the present disclosure .
[Table 1]
Composition S amp1e SiO2 AI2O3 FeOx CaO MgO Na2O T1O2 MnO
Ilmenite 1.06 1.10 12.8 (Fe2C>3) 31.6 (FeO) 0.59 0.35 - 49.5 1.0
Red mud 10.0 23.1 37.4 (Fe2C>3) 6.0 0.3 5.3 7.9 0.1
Table 1 shows the results ilmenite concentrate and red materials according to Examples were analyzed by the energy analysis. Referring to Table ilmenite concentrate and red dioxide component and the iron that the components of mud, which are starting of the present disclosure, dispersive X-ray fluorescence 1, it is confirmed that mud contain the titanium component which are needed for the separation and recovery.
[Table 2]
Composition Sample SiO2 A12O3 FeOx CaO MgO Na2O TiO2 MnO
Titanium dioxide slag after reduction 7.01 1.81 1.97 (Fe2O3) 8.84 (FeO) 0.59 0.35 - 81.8 1.0
Molten oxide 11.5 2.14 14.4 5.5 0.5 5.0 45.2 1.5
Table 2 shows the components of titanium dioxide slag after the melting and reducing step through heating.
Referring to Table 2, all components of iron oxide (FeOx) in the slag after the reduction were determined to be a very little amount of less than 10% compared to the red mud and ilmenite introduced, and thus it is confirmed that the reduction reaction proceeded very effectively.
Also, due to magnetic separation, the iron component greatly decreased and the content of titanium dioxide greatly increased in the titanium dioxide slag after reduction .
In the production process of titanium dioxide, when mixing ilmenite and red mud, heating with a free-burning coal in a rotary furnace and adjusting the reaction temperature, the iron reacted with the free-burning coal again becomes a strong reducing agent and reduces most of iron component to produce molten droplets.
Therefore, since the method of smelting ilmenite utilizing red mud according to the present disclosure utilizes red mud which is waste difficult to treat, it is possible to obtain a high-quality titanium dioxide by smelting a low-quality ilmenite in an environmentally friendly manner.
<Experiment 2> Leaching of alumina and silica according to Beyer process
It was confirmed whether the impurities alumina and silica could be removed from a titanium dioxide slag, in which iron component was reduced and removed by magnetic separation of molten droplets, by adding caustic soda and leaching under a high temperature and high pressure.
There is a problem that red mud contains alumina and silica in addition to iron oxide and they remain after magnetic separation after reduction, therby to increase the load of an acid leaching process and to decrease the quality of titanium dioxide recovered.
is a graph showing alumina and silica contents depending on caustic soda concentration in the Bayer process step in the method of smelting ilmenite using red mud according to another embodiment of the present disclosure .
Referring to FIG. 7, it was confirmed that alumina as well as silica remaining in titanium dioxide slag were removed when the concentration of caustic soda is 2.5 M or higher in case of leaching under the condition of 200 °C
In particular, when the concentration of caustic soda is
2.5 M or higher, the content of alumina and silica can be effectively controlled to 3% by weight or less.
and 20 bar for 1 hour.
Therefore, the method of smelting ilmenite using red mud
according to an embodiment of the present disclosure can
separate and efficiently recover iron component and
titanium dioxide component by using red mud.
Also, the method of smelting ilmenite using red mud according to another embodiment of the present disclosure can utilize red mud which is waste difficult to treat and obtain a variety of by-products, which can be recycled.
In the production process of titanium dioxide, when mixing ilmenite and red mud, heating with a free-burning coal in a rotary furnace and adjusting the reaction temperature, the iron reacted with the free-burning coal again becomes a strong reducing agent and reduces most of iron component to produce molten droplets.
Therefore, since the method of smelting ilmenite utilizing red mud according to the present disclosure utilizes red mud which is waste difficult to treat, it is possible to obtain a high-quality titanium dioxide by smelting a low-quality ilmenite in an environmentally friendly manner.
At this time, if decreasing iron component with a method of separating molten droplets by a magnetic separation, it is possible to obtain a high-quality of titanium dioxide by separating iron component, while decreasing the load of acid-leaching process.
Also, when alumina and silica contained in red mud are concentrated in the reduced titanium dioxide slag, the impurities alumina as well as silica can be removed by introducing into Beyer process and leaching under a high temperature and a high pressure. The alumina to be discharged in crystal may be recovered and reused.
Although specific embodiments of the method of smelting titanium dioxide using ilmenite according to the present disclosure have been described so far, it is apparent that various modifications can be made without departing from the scope of the present disclosure.
Therefore, the scope of the present disclosure should not be limited to the embodiments described, but should be defined by the claims below and equivalents thereof.
In other words, it should be understood that the foregoing embodiments are in all respects as illustrative and not restrictive, and it should be interpreted that the scope of the disclosure is presented by the following claims rather than the detailed description, and that all changes or modifications derived from the meaning and scope of the claims and its equivalent concept should be included in the scope of the present disclosure.

Claims (14)

  1. [Claim 1]
    A method for smelting ilmenite using red mud, comprising the steps of:
    (a) mixing an ilmenite concentrate and red mud to form a mixture;
    (b) adding a carbon source to the mixture, followed by heating to reduce iron in the mixture;
    (c) separating reduced iron through a magnetic separation; and (d) subjecting residue to aeration and acid-leaching to remove iron in the residue and recover titanium dioxide.
  2. [Claim 2]
    The method according to claim 1, characterized in that said ilmenite concentrate contains titanium dioxide (TiCt) in 17 to 50 % by weight.
  3. [Claim 3]
    The method according to claim 1, characterized in that said red mud contains titanium dioxide (TiC>2) in 5 to 10 % by weight.
  4. [Claim 4]
    The method according to claim 1, characterized in that said red mud is added from 10 to 200 parts by weight based on a total of 100 parts by weight of the ilmenite concentrate .
  5. [Claim 5]
    The method according to claim 1, characterized in that, in the step of mixing an ilmenite concentrate and red mud to form a mixture, the mixture is pressurized to form a briquette.
  6. [Claim 6]
    The method according to claim 1, characterized in that said carbon source is any one selected from free-burning coals consisting of peat, brown coal and bituminous coal.
  7. [Claim 7]
    The method according to claim 1, characterized in that said carbon source is added from 10 to 100 parts by weight based on a total of 100 parts by weight of the mixture .
  8. [Claim 8]
    The method according to claim 1, characterized in that said carbon source is added to the mixture, followed by heating at 1350 to 1500 °C for 8 hours to 12 hours to reduce the iron in the mixture.
  9. [Claim 9]
    The method according to claim 1, characterized in that said heating is performed in a sintering furnace or a rotary furnace .
  10. [Claim 10]
    The method according to claim 1, characterized in that said reduced iron is formed in a molten droplet form, which is physically separated through a magnetic force sorting.
  11. [Claim 11]
    The method according to claim 1, characterized in that said residue is subjected to aeration by introducing air for 30 minutes to 30 hours.
  12. [Claim 12]
    The method according to claim 1, characterized in that said acid leaching is performed by using 0.05 to 30 % of sulfuric acid and leaching for 5 minutes to 10 hours to remove iron in the residue.
  13. [Claim 13]
    The method according to claim 1, characterized in that said recovered titanium dioxide has a guality of 88% to 95%.
  14. [Claim 14]
    A method for smelting ilmenite using red mud, comprising the steps of:
    (i) mixing an ilmenite concentrate and red mud to form a mixture;
    (ii) adding a carbon source to the mixture, followed by heating to reduce iron in the mixture to form molten droplets;
    (iii) physically separating the molten droplets to remove the iron and recover a titanium dioxide slag;
    (iv) introducing the titanium dioxide slag into a Bayer process to recover alumina (AI2O3) ; and (v) subjecting the alumina-separated titanium dioxide slag to acid-leaching to remove silica (SiCt) · [Claim 15]
    The method according to claim 14, characterized in that said ilmenite concentrate contains titanium dioxide (T1O2) from 17 to 50 % by weight.
    [Claim 16]
    The method according to claim 14, characterized in that said red mud comprises titanium dioxide (T1O2) , alumina (AI2O3) and silica (SiCh) · [Claim 17]
    The method according to claim 16, characterized in that said titanium dioxide is contained from 5 to 10 % by weight.
    [Claim 18]
    The method according to claim 14, characterized in that red mud is added from 10 to 200 parts by weight for a total of 100 parts by weight of said ilmenite concentrate.
    [Claim 19]
    The method according to claim 14, characterized in that in the step of mixing an ilmenite concentrate and red mud to form a mixture, the mixture is pressurized to form a briquette.
    [Claim 20]
    The method according to claim 14, characterized in that said carbon source is any one selected from free-burning coals consisting of peat, brown coal and bituminous coal.
    [Claim 21]
    The method according to claim 14, characterized in that said carbon source is added from 10 to 100 parts by weight for total 100 parts by weight of said mixture.
    [Claim 22]
    The method according to claim 14, characterized in that the carbon source is added to said mixture, followed by heating at 1400 to 2000 °C for 15 minutes to
    10 hours to reduce iron in the mixture.
    [Claim 23]
    The method according to claim 14, said heating is performed in any one selected from a group consisting of a sintering furnace, a rotary furnace and an arc furnace.
    [Claim 24]
    The method according to claim 14, characterized in that said iron is reduced and formed in a molten droplet form, which is physically separated through a magnetic force sorting or a gravity sorting.
    [Claim 25]
    The method according to claim 14, characterized in that said molten droplet is contained from 25 to 30 % by weight in said reduced matter.
    [Claim 26]
    The method according to 14, characterized in that said Bayer process is performed by adding caustic soda (NaOH) to titanium dioxide slag and leaching alumina at 150 to 200°C and at a pressure of 15 to 20 bar.
    [Claim 27]
    The method according to claim 14, characterized in that said Bayer process is performed by adding 1.25 to 6.25M of caustic soda (NaOH) to titanium dioxide slag to leach alumina .
    [Claim 28]
    The method according to claim 14, characterized in that said acid leaching is performed by using 0.05 to 30 % of sulfuric acid and leaching for 5 minutes to 10 hours to remove iron together with silica remaining in titanium dioxide slag.
    [Claim 29]
    The method according to claim 14, characterized in that said recovered titanium dioxide has a quality of 70% to 97%.
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