WO2008078891A1

WO2008078891A1 - Apparatus and method for manufacturing molten iron

Info

Publication number: WO2008078891A1
Application number: PCT/KR2007/006546
Authority: WO
Inventors: Min-Young Cho; Myoung-Kyun Shin; Hang-Goo Kim; Hoo-Geun Lee; Sang-Hoon Joo
Original assignee: Posco
Priority date: 2006-12-22
Filing date: 2007-12-14
Publication date: 2008-07-03

Abstract

The present invention relates to an apparatus and method for manufacturing molten iron while reusing an offgas of the packed bed reduction reactor and improving energy efficiency. A method for manufacturing molten iron includes i) charging fine ore into at least one fluidized-bed reduction reactor and manufacturing reduced iron; ii) compacting the reduced iron and manufacturing compacted reduced iron; iii) charging the reduced iron into a packed bed reduction reactor and reducing the reduced iron again; iv) charging the re-reduced iron into a melter-gasifier; v) charging lumped carbonaceous materials into the melter- gasifier and forming a coal packed bed in the melter-gasifier; vi) injecting oxygen into the melter-gasifier and combusting the coal packed bed, thereby melting the re-reduced iron and manufacturing molten iron; and vii) supplying an offgas that is discharged from the packed bed reduction reactor to the fluidized-bed reduction reactor.

Description

APPARATUS AND METHOD FOR MANUFACTURING MOLTEN IRON

Technical Field

The present invention relates to an apparatus and method for manufacturing molten iron while reusing an offgas of the packed bed reduction reactor and improving energy efficiency. Background Art

Since a blast furnace method for producing molten iron has many problems such as environment pollution, a smelting reduction process, which can replace the blast furnace method, has been researched. In the smelting reduction process, raw coal is directly used as a fuel and a reducing agent and iron ore is directly used as an iron source, and thereby molten iron is manufactured. After the iron ore is converted into reduced iron in a reduction reactor, the reduced iron is charged into a melter-gasifier. Then, the reduced iron is melted therein, and thereby molten iron is manufactured.

A fluidized-bed reduction reactor is used for reducing iron ore. Iron ore having the shape of fine ore is fluidized in the fluidized-bed reduction reactor while contacting a reducing gas that is injected thereto. Therefore, the iron ore, that is, fine iron ore, is converted into reduced iron and is then discharged from the fluidized-bed reduction reactor. The reduced iron that is discharged from the fluidized-bed reduction reactor is compacted and then charged into a melter-gasifier in order to secure permeability therein.

DISCLOSURE Technical Problem An apparatus for manufacturing molten iron while reusing an offgas of a packed bed reduction reactor and improving energy efficiency is provided, hi addition, a method for manufacturing molten iron using an offgas of the packed bed reduction reactor and improving energy efficiency is provided. Technical Solution

A method for manufacturing molten iron according to an embodiment of the present invention includes i) charging fine ore into at least one fluidized-bed reduction reactor and manufacturing reduced iron; ii) compacting the reduced iron and manufacturing compacted reduced iron; iii) charging the reduced iron into a packed bed reduction reactor and reducing the reduced iron again; iv) charging the re-reduced iron into a melter-gasifier; v) charging lumped carbonaceous materials into the melter- gasifier and forming a coal packed bed in the melter-gasifier; vi) injecting oxygen into the melter-gasifier and combusting the coal packed bed, thereby melting the re-reduced iron and manufacturing molten iron; and vii) supplying an offgas that is discharged from the packed bed reduction reactor to the fluidized-bed reduction reactor.

A method for manufacturing molten iron according to an embodiment of the present invention may further include supplying a reducing gas generated from the melter-gasifier to the fluidized-bed reduction reactor. The reducing gas mixed with the offgas may be supplied to the fluidized-bed reduction reactor in the supplying of the offgas to the fluidized-bed reduction reactor. A method for manufacturing molten iron according to an embodiment of the present invention may further include supplying the reducing gas generated from the melter-gasifier to the packed bed reduction reactor. A temperature of the reducing gas may be in a range from 700⁰C to 900⁰C.

A method for manufacturing molten iron according to an embodiment of the present invention may further include reforming the reducing gas after mixing the offgas with the reducing gas. The reducing gas mixed with the offgas may be reformed by combusting the reducing gas with oxygen or a hydrocarbon gas.

The offgas may be reformed to be supplied to the fluidized-bed reduction reactor in the supplying of the offgas to the fluidized-bed reduction reactor. The offgas may be reformed by removing carbon dioxide from the offgas. The offgas may be reformed by combusting the offgas with oxygen or a hydrocarbon gas.

A method for manufacturing molten iron according to an embodiment of the present invention may further include supplying the reducing gas generated from the melter-gasifier to the fluidized-bed reduction reactor. The supplying of the offgas to the fluidized-bed reduction reactor may further include reforming the reducing gas after mixing the reducing gas with the offgas. The reducing gas that is mixed with the offgas may be reformed by combusting the reducing gas with oxygen or a hydrocarbon gas.

A method for manufacturing molten iron according to an embodiment of the present invention may further include supplying the reducing gas generated from the melter-gasifier to the fluidized-bed reduction reactor. The reducing gas may be mixed with the offgas after the reducing gas is reformed by combusting the reducing gas with oxygen or a hydrocarbon gas in the supplying of the reducing gas to the fluidized-bed reduction reactor.

A method for manufacturing molten iron according to an embodiment of the present invention may further include drying the fine ore by supplying the offgas to the fine ore before charging the fine ore into the fluidized-bed reduction reactor. A reducing ratio of the reduced iron may be 11% or more in the manufacturing of the reduced iron. The reducing ratio of the reduced iron may be 20% or more. A temperature of the gas entering the fluidized-bed reduction reactor may be 450 °C or more in the supplying of the offgas to the fluidized-bed reduction reactor. A method for manufacturing molten iron according to an embodiment of the present invention may further include charging lumped ore into the packed bed reduction reactor. An apparatus for manufacturing molten iron according to an embodiment of the present invention includes i) at least one fluidized-bed reduction reactor that reduces fine ore and manufactures reduced iron; ii) an apparatus for manufacturing compacted iron that is connected to the fluidized-bed reduction reactor and compacts the reduced iron; iii) a packed bed reduction reactor that is connected to the apparatus for manufacturing compacted iron and reduce the reduced iron again; iv) a melter-gasifier into which the re-reduced iron is charged and oxygen is injected; and v) an offgas supply line that supplies offgas that is discharged from the packed bed reduction reactor to the fluidized-bed reduction reactor. A coal packed bed is formed by charging lumped carbonaceous materials into the melter- gasifier that is connected to the packed bed reduction reactor. The oxygen combusts the coal packed bed and then melts the re-reduced iron, and thereby the melter-gasifier manufactures molten iron.

An apparatus for manufacturing molten iron according to an embodiment of the present invention may further include a reducing gas supply line that is connected to the melter-gasifier and the fluidized-bed reduction reactor to supply the reducing gas that is discharged from the melter-gasifier to the fluidized-bed reduction reactor. The offgas supply line may communicate with the reducing gas supply line. The apparatus for manufacturing molten iron according to an embodiment of the present invention may further include a gas reformer that is installed in the reducing gas supply line to reform the reducing gas mixed with the offgas. The gas reformer may reform the reducing gas by combusting the reducing gas with oxygen or a hydrocarbon gas.

An apparatus for manufacturing molten iron according to an embodiment of the present invention may further include a gas reformer that is installed in the reducing gas supply line to reform a reducing gas before the reducing gas is mixed with the offgas. The gas reformer may reform the reducing gas by combusting the reducing gas with oxygen or a hydrocarbon gas.

An apparatus for manufacturing molten iron according to an embodiment of the present invention may further include a reducing gas supply line that supplies the reducing gas that is discharged from the melter- gasifier to the packed bed reduction reactor. A temperature of the reducing gas may be in a range from 700 ^°C to 900 ^°C .

An apparatus for manufacturing molten iron according to an embodiment of the present invention may further include a gas reformer that is installed in the offgas supply line to reform the offgas. The gas reformer may reform the offgas by removing carbon dioxide from the offgas. The gas reformer may reform the offgas by combusting the offgas with oxygen or a hydrocarbon gas.

An apparatus for manufacturing molten iron according to an embodiment of the present invention may further include a reducing gas supply line that is connected to the melter-gasifier and the fluidized-bed reduction reactor to supply the reducing gas that is discharged from the melter-gasifier to the fluidized-bed reduction reactor. The offgas supply line may communicate with the reducing gas supply line, and another gas reformer may be installed in the reducing gas supply line to reform the reducing gas mixed with the offgas. The other gas reformer may reform the reducing gas mixed with the offgas by combusting the reducing gas with oxygen or a hydrocarbon gas.

An apparatus for manufacturing molten iron according to an embodiment of the present invention may further include a fine ore dryer that is connected to the offgas supply line and the fluidized-bed reduction reactor, and dries the fine ore with the offgas. A reducing ratio of the reduced iron may be 11% or more. A reducing ratio of the reduced iron may be 20% or more. A temperature of a gas entering into the fluidized-bed reduction reactor may be 450⁰C or more. Lumped ore may be charged into the packed bed reduction reactor. Advantageous Effects

As described above, since an offgas that is discharged from the packed bed reduction reactor is supplied to the fluidized-bed reduction reactor and thereby fine iron ore is reduced, energy efficiency can be improved.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of an apparatus for manufacturing molten iron according to a first embodiment of the present invention.

FIG. 2 is a schematic view of an apparatus for manufacturing molten iron according to a second embodiment of the present invention.

FIG. 3 is a schematic view of an apparatus for manufacturing molten iron according to a third embodiment of the present invention. FIG. 4 is a schematic view of an apparatus for manufacturing molten iron according to a fourth embodiment of the present invention.

FIG. 5 is a schematic view of an apparatus for manufacturing molten iron according to a fifth embodiment of the present invention. FIG. 6 is a schematic view of an apparatus for manufacturing molten iron according to a sixth embodiment of the present invention.

BEST MODE

Exemplary embodiments of the present invention will be explained in detail below with reference to the attached drawings in order for those skilled in the art of the field of the present invention to easily perform the present invention. However, the present invention can be realized in various forms and is not limited to the embodiments explained below. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. All terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and/ or sections, these elements, components, regions, layers, and/ or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another element, component, region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present invention.

FIG. 1 schematically shows an apparatus for manufacturing molten iron 100 according to a first embodiment of the present invention. In FIG. 1, transferring path of the iron ore is represented by solid lines, that of the gas is represented by thin lines, and that of the coal is represented by dotted lines.

As shown in FIG. 1, the apparatus for manufacturing molten iron 100 manufactures molten iron by using fine ore and lumped ore as iron ore. Lumped carbonaceous materials are used for melting iron ore. The lumped carbonaceous materials and reduced iron are charged into the melter-gasifier

40 and molten iron is manufactured.

The apparatus for manufacturing molten iron 100 includes a fine ore dryer 50, a fluidized-bed reduction reactor 20, an apparatus for manufacturing compacted iron 30, a packed bed reduction reactor 130, and a melter-gasifier 40. In addition, the apparatus for manufacturing molten iron 100 may further include other devices as necessary.

Fine ore and lumped ore can be used in the apparatus for manufacturing molten iron 100. Here, a grain size of the lumped ore is greater than that of the fine ore. After the fine ore is dried in the fine ore dryer 50, it is charged into the fluidized-bed reduction reactor 20. The lumped ore is directly charged into the packed bed reduction reactor 130.

The fine ore is fluidized to be reduced while passing through the fluidized-bed reduction reactor 20. When the grain size of the fine ore is large and a flow velocity of a reducing gas in the fluidized-bed reduction reactor 20 is low, the fine ore does not fluidize well in the fluidized-bed reduction reactor 20. Therefore, since the fine ore may sink to the bottom of the fluidized-bed reduction reactor 20 and then solidify into agglomerates, the fine ore should have a grain size that is sufficient to not be scattered but that is capable of being fluidized in the fluidized-bed reduction reactor 20. After the fine ore is reduced in the fluidized-bed reduction reactor 20 and is then converted into reduced iron, it is compacted in the apparatus for manufacturing compacted iron 30. Next, the fine ore is charged into the packed bed reduction reactor 130 and is further reduced. Meanwhile, lumped ore is charged into the packed bed reduction reactor 130 to be reduced together with the compacted reduced iron that is compacted in the apparatus for manufacturing compacted iron 30. The lumped ore and reduced iron that are reduced in the packed bed reduction reactor 130 are charged into the melter-gasifier 140 and are then melted therein. A grain size of the lumped ore charged into the packed bed reduction reactor 130 is determined within a range in which permeability deterioration is not over the operating limit. For example, a grain size of the second iron ore can be 5mm or more. If the grain size of the second iron ore is less than 5mm, a space that is capable of passing the reducing gas rising from a lower side of the packed bed reduction reactor 130 is too small when it is charged into the packed bed reduction reactor 130. Therefore, it blocks the flow of the reducing gas and then operation becomes unstable. Pellets or sintered ore can be charged into the packed bed reduction reactor 130 in addition to lumped ore. Accordingly, an operation using the apparatus for manufacturing molten iron 100 can be more stable.

The fine ore dryer 50 dries the fine ore to charge it into the fluidized- bed reduction reactor 20. Since the fine ore is collected from a production site, it has much moisture. Therefore, the fine ore is dried, and thereby moisture contained in the fine ore is minimized. As a result, a phenomenon in which the fine ore sticks to the inner sides of the fluidized-bed reduction reactor 20 that is caused by the moisture can be prevented. A plurality of fluidized-bed reduction reactors 20 are connected to each other in a multi-stage manner. Although two fluidized-bed reduction reactors 201 and 203 are shown in FIG. 1, a single fluidized-bed reduction reactor or three or more fluidized-bed reduction reactors may be used. The fine ore, which is charged into the fluidized-bed reduction reactor 20, is reduced while passing through the fluidized-bed reduction reactor 20. Additives can be charged into the fluidized-bed reduction reactor 20 together with the fine ore in order to prevent the fine ore from sticking to the inner side of the fluidized-bed reduction reactor 20 if necessary. The reducing gas generated from the melter-gasifier 140 consequently passes through a plurality of fluidized-bed reduction reactors 20 and is then discharged to the outside. The fine ore charged into the first fluidized-bed reduction reactor 201 is preheated and the preheated fine ore is charged into the second fluidized-bed reduction reactor 203 and then pre-reduced. The fine ore is finally reduced in the packed bed reduction reactor 10 after being reduced in the fluidized-bed reduction reactor 20.

A reducing ratio of the fine ore in the fluidized-bed reduction reactor 20 may be a minimized reducing ratio capable of compacting the fine ore in the apparatus for manufacturing compacted iron 30. For example, the reducing ratio of the fine ore may be 11% or more. The reducing ratio of 11% is a value that is obtained when hematite ore is reduced to magnetite ore, and most of the reducing differentiation occurs in this case. Preferably, the reducing ratio of the fine ore may be 20% or more. If a reducing ratio is 20% or more, reducing differentiation in the packed bed reduction reactor 130 can be minimized since it means that most of the hematite ore is converted into magnetite ore. If a reducing ratio of the fine ore is too low, it is difficult to compact it in the apparatus for manufacturing compacted iron 30. This is because an amount of pure iron, which can act as a binder during compression, is too low. As a result, the fine ore is not compacted well and is easily broken. On the contrary, if the reducing ratio of the fine ore is too high, the fine ore can stick to the inner side of the fluidized-bed reduction reactor 130. Therefore, for example, the reducing ratio of the fine ore in the fluidized-bed reduction reactor 130 may be 90% or less.

The reduced iron, which is manufactured while passing through the fluidized-bed reduction reactor 20, is compacted in the apparatus for manufacturing compacted iron 30. The apparatus for manufacturing compacted iron 30 is connected to the fluidized-bed reduction reactor 20. The apparatus for manufacturing compacted iron 30 includes a hopper 302, a pair of rolls 304, and a crusher 306. The apparatus for manufacturing compacted iron 30 may further include other devices if necessary.

The apparatus for manufacturing compacted iron 30 compresses the reduced iron by the pair of rolls 304, thereby compacting the reduced iron. The compacted reduced iron is crushed by the crusher 306 and is then transferred to the packed bed reduction reactor 130. The reduced iron compacted in the apparatus for manufacturing compacted iron 30 is charged into the packed bed reduction reactor 10 after passing through a hot pressure equalizing device 101. Lumped ore is also charged into the packed bed reduction reactor 10. The lumped ore and compacted iron may be simultaneously or alternately charged into the packed bed reduction reactor 10.

The lumped ore and compacted iron charged into the packed bed reduction reactor 10 are reduced together in a sufficient time. A time for reducing the compacted iron and the lumped ore in the packed bed reduction reactor 10 can be longer than that for reducing the fine ore in the fluidized-bed reduction reactor 20. Therefore, the lumped ore and the compacted iron are reduced, for example, with a reducing ratio of 70% or more, and thereby a fuel ratio of the melter-gasifier 140 can be minimized.

The lumped ore and compacted iron reduced in the packed bed reduction reactor 130 are charged into the melter-gasifier 140. Meanwhile, lumped carbonaceous materials containing volatile matter as a heat source for melting the lumped ore and compacted iron are charged into the melter- gasifier 140. Coal briquettes or lumped coal as lumped carbonaceous materials may be used. The coal briquettes or lumped coal is charged into the melter-gasifier 40, thereby forming a coal packed bed therein. A reducing gas generated by combusting the lumped carbonaceous materials is supplied to the packed bed reduction reactor 130 and the fluidized-bed reduction reactor 20 through reducing gas supply lines LlO and L40, respectively. Therefore, the fluidized-bed reduction reactor 20 and the packed bed reduction reactor 130 can reduce iron ore by using the reducing gas.

Since the compacted reduced iron having a predetermined reducing ratio, for example a mean reducing ratio of 45%, are charged into the packed bed reduction reactor 130, a reducing load of the reducing gas supplied to the packed bed reduction reactor 130 is low. Therefore, the offgas that is discharged from the packed bed reduction reactor 130 through an offgas supply line L12 also still has a high reducing ratio. Further, since the temperature of the offgas is high, for example in a range from 500⁰C to 600⁰C, the offgas is supplied to the fluidized-bed reduction reactor 20 without collecting dust from the offgas by spraying the offgas with water in order to reduce a loss of energy. As a result, a reducing ratio of the fine ore in the fluidized-bed reduction reactor 20 can be improved. The temperature of the reducing gas supplied to the packed bed reduction reactor 130 can be in a range from 700 °C to 850⁰C. If the temperature of the reducing gas supplied to the packed bed reduction reactor 130 is too low, a fuel ratio for melting the reduced iron in the melter- gasifier 140 is increased since the reduced iron cannot be reduced due to a declined reducing ratio. In addition, if the temperature of the reducing gas is too high, the reduced iron can stick to the inner side of the packed bed reduction reactor 130.

As shown in FIG. 1, the offgas supply line L12 may communicate with the reducing gas supply line L14. Therefore, the reducing gas mixed with the offgas is mixed can be supplied to the fluidized-bed reduction reactor 20. The reducing gas is mixed with the offgas, and thereby the temperature of the reducing gas can be suitably lowered and a reducing ratio of the reducing gas can be suitably controlled. For example, the temperature of the reducing gas generated from the melter-gasifier 140 and supplied through the reducing gas supply line L40 is about 1000⁰C. Then, the temperature of the reducing gas can be lowered to a range from 700 °C to 850 ^°C by mixing the offgas with the reducing gas. Therefore, a gas with a temperature in a range from 700⁰C to 850⁰C enters into a second fluidized- bed reduction reactor 203. If the temperature of the reducing gas is too low, a reducing ratio may be lowered. If the temperature of the reducing gas is too high, the fine ore can stick to the inner side of the fluidized-bed reduction reactor 20. Since the temperature of the reducing gas has been lowered while the reducing ratio thereof is suitably maintained, the fine ore is prevented from sticking to the inner side of the fluidized-bed reduction reactor 20 due to the hot reducing gas.

FIG. 2 schematically shows an apparatus for manufacturing molten iron 200 according to an embodiment of the present invention. Since the

1 ] apparatus for manufacturing molten iron 200 of FIG. 2 is the same as the apparatus for manufacturing molten iron 100 of FIG. 1 except a first gas reformer 60, like reference numerals refer to like elements and a detailed description thereof is omitted. As shown in FIG. 2, the first gas reformer 60 is installed in a reducing gas supply line L40. The reducing gas mixed with the offgas is reformed to be supplied to the second fluidized-bed reduction reactor 203. The first gas reformer 60 controls the temperature and elements of the reducing gas in order to effectively reduce the fine ore fluidizing in the fluidized-bed reduction reactor 20. When the reducing is mixed with the offgas, the temperature thereof can be lowered due to the offgas. Therefore, the reducing gas is partly combusted by injecting a fuel such as oxygen or a hydrocarbon gas by using the first gas reformer 60. For example, the temperature of the reformed reducing gas can be 500⁰C or more. As a result, the temperature of the reducing gas can be raised by using combustion heat of the oxygen while a reducing power of the reducing gas can be suitably maintained.

FIG. 3 schematically shows an apparatus for manufacturing molten iron 300 according to a third embodiment of the present invention. Since the apparatus for manufacturing molten iron 300 of FIG. 3 is the same as the apparatus for manufacturing molten iron 200 of FIG. 2 except a second gas reformer 70, like reference numerals refer to like elements and a detailed description thereof is omitted.

A large amount of carbon dioxide is contained in an offgas that is discharged from the packed bed reduction reactor 130. Since reducing power of the offgas is reduced due to the carbon dioxide, the carbon dioxide is removed by using the second gas reformer 70. Since the offgas with a raised reducing power can be supplied to the second fluidized-bed reduction reactor 203 by using the second gas reformer 70, the reducing ratio of the fine ore can be increased.

FIG. 4 schematically shows an apparatus for manufacturing molten iron 400 according to a fourth embodiment of the present invention. Since the apparatus for manufacturing molten iron 400 of FIG. 4 is the same as the apparatus for manufacturing molten iron 200 of FIG. 2 except a third gas reformer 80, like reference numerals refer to like elements and a detailed description thereof is omitted. As shown in FIG. 4, a reducing gas can be reformed by using the third gas reformer 80 before being mixed with the offgas flowing through an offgas supply line L12. A temperature of the reducing gas can be suitably raised by reforming the reducing gas by combusting it. Therefore, a reducing power of the reducing gas can be suitably maintained even if the reducing gas supply line L40 is connected to the offgas supply line L12 and then the offgas is mixed with the reducing gas.

FIG. 5 schematically shows an apparatus for manufacturing molten iron 500 according to a fifth embodiment of the present invention. Since the apparatus for manufacturing molten iron 500 of FIG. 5 is the same as the apparatus for manufacturing molten iron 300 of FIG. 3 except a gas line for drying L42, like reference numerals refer to like elements and a detailed description thereof is omitted.

As shown in FIG. 5, the gas line for drying L42 is connected to the offgas supply line L12, thereby supplying offgas to the fine ore dryer 50. Therefore, fine ore charged into the fine ore dryer 50 can be dried by using the offgas. Generally, although coke oven gas (COG) is used for drying fine ore in the fine ore dryer 50, the coke oven gas can be replaced by the offgas in the fifth embodiment of the present invention. Therefore, energy efficiency is improved. FIG. 6 schematically shows an apparatus for manufacturing molten iron 600 according to a sixth embodiment of the present invention. Since the apparatus for manufacturing molten iron 600 of FIG. 6 is the same as the apparatus for manufacturing molten iron 300 of FIG. 3, like reference numerals refer to like elements and a detailed description thereof is omitted. As shown in FIG. 6, a reducing gas is supplied to the packed bed reduction reactor 130 from the melter-gasifier 140 through a reducing gas supply line LlO. The packed bed reduction reactor 130 reduces lumped ore by the reducing gas and then reduces the reduced iron again. The offgas is discharged from the packed bed reduction reactor 130 and is then directly supplied to the fluidized-bed reduction reactor 20 through an offgas supply line L14. The offgas passes through the second and first gas reformers 70 and 60. Carbon dioxide can be removed from the offgas by using the second gas reformer 70, and the offgas can be partly combusted by injecting a fuel such as oxygen or a hydrocarbon gas using the first gas reformer 60. Therefore, after a reducing power of the offgas is raised, the offgas is supplied to the fluidized-bed reduction reactor 20, and thereby fine ore can be effectively reduced in the fluidized-bed reduction reactor 20.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

CLAIM

1. A method for manufacturing molten iron, the method comprising: charging fine ore into at least one fluidized-bed reduction reactor and manufacturing reduced iron; compacting the reduced iron and manufacturing compacted reduced iron; charging the reduced iron into a packed bed reduction reactor and reducing the reduced iron again; charging the re-reduced iron into a melter-gasifier; charging lumped carbonaceous materials into the melter-gasifier and forming a coal packed bed in the melter-gasifier; injecting oxygen into the melter-gasifier and combusting the coal packed bed, thereby melting the re-reduced iron and manufacturing molten iron; and supplying an offgas that is discharged from the packed bed reduction reactor to the fluidized-bed reduction reactor.

2. The method of Claim 1, further comprising supplying a reducing gas generated from the melter-gasifier to the fluidized-bed reduction reactor, wherein the reducing gas mixed with the offgas is supplied to the fluidized-bed reduction reactor in the supplying of the offgas to the fluidized-bed reduction reactor.

3. The method of Claim 2, further comprising supplying the reducing gas generated from the melter-gasifier to the packed bed reduction reactor.

4. The method of Claim 3, wherein a temperature of the reducing gas is in a range from 700 °C to 900 °C .

5. The method of Claim 2, further comprising reforming the reducing gas after mixing the offgas with the reducing gas.

6. The method of Claim 5, wherein the reducing gas mixed with the offgas is reformed by combusting the reducing gas with oxygen or a hydrocarbon gas.

7. The method of Claim 1, wherein the offgas is reformed to be supplied to the fluidized-bed reduction reactor in the supplying of the offgas to the fluidized-bed reduction reactor.

8. The method of Claim 7, wherein the offgas is reformed by removing a carbon dioxide from the offgas.

9. The method of Claim 7, wherein the offgas is reformed by combusting the offgas with oxygen or a hydrocarbon gas.

10. The method of Claim 7, further comprising supplying the reducing gas generated from the melter-gasifier to the fluidized-bed reduction reactor, wherein the supplying of the offgas to the fluidized-bed reduction reactor further comprises reforming the reducing gas after mixing the reducing gas with the offgas.

11. The method of Claim 10, wherein the reducing gas mixed with the offgas is reformed by combusting the reducing gas with oxygen or a hydrocarbon gas.

12. The method of Claim 7, further comprising supplying the reducing gas generated from the melter-gasifier to the fluidized-bed reduction reactor, wherein the reducing gas is mixed with the offgas after the reducing gas is reformed by combusting the reducing gas with oxygen or a hydrocarbon gas in the supplying of the reducing gas to the fluidized-bed reduction reactor.

13. The method of Claim 1, further comprising drying the fine ore by supplying the offgas to the fine ore before charging the fine ore into the fluidized-bed reduction reactor.

14. The method of Claim 1, wherein a reducing ratio of the reduced iron is 11% or more in the manufacturing of reduced iron.

15. The method of Claim 14, wherein the reducing ratio of the reduced iron is 20% or more.

16. The method of Claim 1, wherein a temperature of the gas entering into the fluidized-bed reduction reactor is 450⁰C or more in the supplying of the offgas to the fluidized-bed reduction reactor.

17. The method of Claim 1, further comprising charging lumped ore into the packed bed reduction reactor.

18. An apparatus for manufacturing molten iron, the apparatus comprising: at least one fluidized-bed reduction reactor that reduces fine ore and manufactures reduced iron; an apparatus for manufacturing compacted iron that is connected to the fluidized-bed reduction reactor and compacts the reduced iron; a packed bed reduction reactor that is connected to the apparatus for manufacturing compacted iron and reduce the reduced iron again; a melter-gasifier into which the re-reduced iron is charged and oxygen is injected, in which a coal packed bed is formed by charging lumped carbonaceous materials thereto, and that is connected to the packed bed reduction reactor; and an offgas supply line that supplies offgas that is discharged from the packed bed reduction reactor to the fluidized-bed reduction reactor, wherein the oxygen combusts the coal packed bed and then melts the re-reduced iron, and thereby the melter-gasifier manufactures molten iron.

19. The apparatus of Claim 18, further comprising a reducing gas supply line that is connected to the melter-gasifier and the fluidized-bed reduction reactor to supply the reducing gas that is discharged from the melter-gasifier to the fluidized-bed reduction reactor.

20. The apparatus of Claim 19, wherein the offgas supply line communicates with the reducing gas supply line.

21. The apparatus of Claim 20, further comprising a gas reformer that is installed in the reducing gas supply line to reform the reducing gas mixed with the offgas.

22. The apparatus of Claim 21, wherein the gas reformer reforms the reducing gas by combusting the reducing gas with oxygen or a hydrocarbon gas.

23. The apparatus of Claim 20, further comprising a gas reformer that is installed in the reducing gas supply line to reform a reducing gas before the reducing gas is mixed with the offgas, wherein the gas reformer reforms the reducing gas by combusting the reducing gas with oxygen or a hydrocarbon gas.

24. The apparatus of Claim 18 further comprising a reducing gas supply line that supplies the reducing gas that is discharged from the melter- gasifier to the packed bed reduction reactor.

25. The apparatus of Claim 24, wherein a temperature of the reducing gas is in a range from 700⁰C to 900⁰C .

26. The apparatus of Claim 18, further comprising a gas reformer that is installed in the offgas supply line to reform the offgas.

27. The apparatus of Claim 26, wherein the gas reformer reforms the offgas by removing carbon dioxide from the offgas.

28. The apparatus of Claim 26, wherein the gas reformer reforms the offgas by combusting the offgas with oxygen or a hydrocarbon gas.

29. The apparatus of Claim 26, further comprising a reducing gas supply line that is connected to the melter-gasifier and the fluidized-bed reduction reactor to supply the reducing gas that is discharged from the melter-gasifier to the fluidized-bed reduction reactor, wherein the offgas supply line communicates with the reducing gas supply line, and wherein another gas reformer is installed in the reducing gas supply line to reform the reducing gas mixed with the offgas.

30. The apparatus of Claim 29, wherein the other gas reformer reforms the reducing gas mixed with the offgas by combusting the reducing gas with oxygen or a hydrocarbon gas.

31. The apparatus of Claim 18, further comprising a fine ore dryer that is connected to the offgas supply line and the fluidized-bed reduction reactor, and that dries the fine ore by the offgas.

32. The apparatus of Claim 18, wherein a reducing ratio of the reduced iron is 11% or more.

33. The apparatus of Claim 32, wherein a reducing ratio of the reduced iron is 20% or more.

34. The apparatus of Claim 18, wherein a temperature of a gas entering into the fluidized-bed reduction reactor is 450 °C or more.

35. The apparatus of Claim 18, wherein lumped ore is charged into the packed bed reduction reactor.