WO2008078938A1

WO2008078938A1 - Apparatus for manufacturing molten iron and method for manufacturing molten iron

Info

Publication number: WO2008078938A1
Application number: PCT/KR2007/006775
Authority: WO
Inventors: Jun-Hyuk Lee; Hang-Goo Kim; Myoung-Kyun Shin; Min-Young Cho
Original assignee: Posco
Priority date: 2006-12-26
Filing date: 2007-12-24
Publication date: 2008-07-03
Also published as: CN101568650A; CN101568650B; KR100840231B1

Abstract

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 and plasticizes fine iron; ii) an apparatus for manufacturing compacted iron that molds the fine iron and manufactures compacted iron; iii) a melter-gasifier into which the compacted iron is charged and oxygen is injected; iv) a reducing gas supply line that supplies reducing gas discharged from the melter-gasifier to the fluidized-bed reduction reactor; and v) a fine particle injecting device that injects viscosity reducing materials into the reducing gas such that viscosity of dust contained in the reducing gas is reduced. The melter-gasifier manufactures molten iron.

Description

APPARATUS FOR MANUFACTURING MOLTEN IRON AND METHOD FOR MANUFACTURING MOLTEN IRON

Technical Field The present invention relates to an apparatus for manufacturing molten iron and a method for manufacturing molten iron, and more specifically to an apparatus for manufacturing molten iron and a method for manufacturing molten iron using raw coal and fine iron ore. Background Art The iron and steel industry is a core industry that supplies the basic materials needed in construction and in the manufacture of automobiles, ships, home appliances, and many other products we use. It is also an industry with one of the longest histories that has progressed together with humanity. In an iron foundry, which plays a pivotal roll in the iron and steel industry, after molten iron, which is pig iron in a molten state, is produced by using iron ore and coal as raw materials, steel is produced from the molten iron and then supplied to customers.

Currently, approximately 60% of the world's iron production is produced using a blast furnace method that has been in development since the 14th century. According to the blast furnace method, iron ore that has gone through a sintering process and coke that is produced using bituminous coal as a raw material are charged into a blast furnace together, and oxygen is supplied thereto to reduce the iron ore to iron, thereby manufacturing molten iron. The blast furnace method, which is the most popular in plants for manufacturing molten iron, requires that raw materials have strength of at least a predetermined level and have grain sizes that can ensure permeability in the furnace, taking into account reaction characteristics. For that reason, as described above, coke that is obtained by processing specific raw coal is used as a carbon source to be used as a fuel and as a reducing agent. Also, sintered ore that has gone through a successive agglomerating process is mainly used as an iron source. Accordingly, the modern blast furnace method requires raw material preliminary processing equipment, such as coke manufacturing equipment and sintering equipment. That is, it is necessary to be equipped with subsidiary facilities in addition to the blast furnace, and to also have equipment for preventing and minimizing pollution generated from the subsidiary facilities. Therefore, there is a problem in that a heavy investment in the additional facilities and equipment leads to increased manufacturing costs.

In order to solve these problems with the blast furnace method, significant effort has been made in iron works all over the world to develop a smelting reduction process that produces molten iron by directly using raw coal as a fuel and a reducing agent and by directly using fine ore, which accounts for more than 80% of the world's ore production.

The apparatus for manufacturing molten iron according to a smelting reduction process includes a fluidized-bed reduction reactor in which a bubble fluidized-bed is formed, and a melter-gasifier in which a coal packed bed is formed. The melter-gasifier is connected to the fluidized-bed reduction reactor. In this case, fine iron ore and additives at room temperature are charged into the fluidized-bed reduction reactor to be pre- reduced. A reducing gas used for fluidizing and reducing the fine iron ore in the fluidized-bed reduction reactor is generated from the melter-gasifier and is supplied.

A high temperature operation of 1000 °C or more is used in an upper portion of the melter-gasifier. A large amount of dust is generated by combustion, thermal differentiation, and compaction of the coal that is charged into the melter-gasifier and in thermal differentiation of the direct reduced iron. In this case, although most of the generated dust is absorbed into a coal packed bed, the dust partly enters into the fluidized-bed reduction reactor through a reducing gas supply line while flowing by an updraft stream of the reducing gas rising from a lower side of the melter-gasifier.

However, since the dust generated from the melter-gasifier has a viscosity, it sticks to a distribution plate or a cyclone of the fluidized-bed reduction reactor if it enters into the fluidized-bed reduction reactor. Therefore, if a large amount of dust having a strong viscosity enters into the fluidized-bed reduction reactor, nozzles of the distribution plate of the fluidized-bed reduction reactor are blocked, a load to the cyclone in the fluidized-bed reduction reactor is increased, and the cyclone is blocked. Furthermore, if the dust sticks to the fine iron ore fluidizing in the fluidized- bed reduction reactor, it causes an unstable operation such as formation of a stagnated layer.

DISCLOSURE Technical Problem

An apparatus for manufacturing molten iron is provided to secure operational stability of the fluidized-bed reduction reactor by reducing viscosity of the dust, and increase productivity and operating ratio of the installation in the overall process. In addition, a method for manufacturing molten iron using the above-described apparatus for manufacturing molten iron is provided. Technical Solution

An apparatus for manufacturing molten iron according to an embodiment of the present invention includes at least one fluidized-bed reduction reactor that reduces and plasticizes fine iron; an apparatus for manufacturing compacted iron that molds the fine iron and manufactures compacted iron; a melter-gasifier into which the compacted iron is charged and oxygen is injected; a reducing gas supply line that supplies reducing gas discharged from the melter-gasifier to the fluidized-bed reduction reactor; and a fine particle injecting device that injects viscosity reducing materials into the reducing gas such that viscosity of dust contained in the reducing gas is reduced. The melter-gasifier manufactures molten iron.

An apparatus for manufacturing molten iron may further include a reducing gas flow line that is connected to an upper side of the melter- gasifier, and a cyclone to which the reducing gas is supplied from the reducing gas flow line connected thereto. The cyclone may collect dust in the reducing gas. In addition, an apparatus for manufacturing molten iron may further include a dust storage bin that is connected to a lower side of the cyclone and restores the dust collected in the cyclone and recharge the dust into the melter-gasifier.

The fine particle injecting device may be connected to the reducing gas flow line by a gas transferring line that transfers the viscosity reducing materials to the reducing gas supply line by a gas. The gas transferring line may be connected to the reducing gas flow line in a position that is closer to the melter-gasifier than to the cyclone.

The viscosity reducing materials may be coke dry quenching (CDQ) dust. In addition, the viscosity reducing materials may be MgO powder, CaO powder, or SiO₂ powder.

Meanwhile, a method for manufacturing molten iron according to a present invention includes i) reducing and plasticizing fine iron in a fluidized-bed reduction reactor; ii) compacting the reduced and plasticized fine iron; iii) charging the compacted fine iron into a melter-gasifier; iv) supplying a reducing gas generated from the melter-gasifier to the fluidized- bed reduction reactor; and v) lowering viscosity of the dust in the reducing gas by supplying viscosity reducing materials to the reducing gas.

The method for manufacturing molten iron may further include collecting the dust in the reducing gas that is generated from the fluidized- bed reduction reactor by using a cyclone. In addition, the method for manufacturing molten iron may further include restoring the collected dust and recharging the collected dust into the melter-gasifier. The viscosity reducing materials may be injected between the melter-gasifier and the cyclone. In this case, the viscosity reducing materials may be injected at a position that is closer to the melter-gasifier than to the cyclone.

The viscosity reducing materials may be coke dry quenching (CDQ) dust. The coke dry quenching (CDQ) dust may be injected into the reducing gas such that an amount of carbon contained in the dust is not more than 60%.

In addition, the viscosity reducing materials may be MgO powder, CaO powder, or SiO₂ powder. The viscosity reducing materials may be injected to be in a range from 2wt% to 10wt% of the dust. Advantageous Effects

Since the viscosity of the dust generated from the melter-gasifier is suppressed, nozzles of the distribution plate and a cyclone of the fluidized- bed reduction reactor are not blocked. In addition, formation of a stagnating layer above the distribution plate of the fluidized-bed reduction reactor, which is formed by the sticky dust, is suppressed.

DESCRIPTION OF DRAWINGS

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

FIG. 2 is a schematic inner cross-sectional view magnifying a portion II of FIG. 1.

BEST MODE

Exemplary embodiments of the present invention will be explained in detail below with reference to the attached drawings. The embodiments of the present invention are merely to illustrate the present invention, and the present invention is not limited thereto.

FIG. 1 schematically shows an apparatus for manufacturing compacted iron 1000 according to an embodiment of the present invention. A structure of the apparatus for manufacturing molten iron 1000 shown in FIG. 1 is merely to illustrate the present invention, and the present invention is not limited thereto. Therefore, the apparatus for manufacturing molten iron 1000 may be formed as other structures and may further include other devices. As shown in FIG. 1, the apparatus for manufacturing molten iron

1000 includes a fluidized-bed reduction reactor 10 as a reduction reactor, an apparatus for restoring fine iron 20, an apparatus for manufacturing compacted iron 30, a melter-gasifier 40, a reducing gas supply line 50, and a fine particle supplying device 70. In addition, the apparatus for manufacturing molten iron 1000 further includes a hot pressure equalizing device 60 connected between the apparatus for manufacturing compacted iron 30 and the melter-gasifier 40, a cyclone 80 connected to the melter- gasifier 40 through a reducing gas flow line 82, and a dust storage bin 90 connected to a lower side of the cyclone 80. The apparatus for manufacturing molten iron 1000 may further include other devices necessary for manufacturing molten iron. A fluidized-bed is formed in fluidized-bed reduction reactors 10 that are connected to each other in order to reduce fine iron ore and so on. A reducing gas discharged from a coal packed bed in the melter-gasifier 40 is supplied to each of the fluidized-bed reduction reactors 10 through the reducing gas supply line 50. The reducing gas flows in the fluidized-bed reduction reactor 10 and reduces the fine iron ore. In this case, additives can be used by mixing them with the fine iron ore. As shown in FIG. 1, the fluidized-bed reduction reactor 10 includes a preheating reduction reactor 10a, a first reduction reactor 10b, a second reduction reactor 10c, and a final reduction reactor 1Od. After the temperature of the reducing gas generated from the melter- gasifier 40 is raised by the burners 12a, 12b, and 12c for raising gas temperature in order to compensate lost heat before the reduced gas is supplied to fluidized-bed reduction reactors 10b, 10c, and 1Od excluding a preheating reduction reactor 10a, the reducing gas is supplied to the fluidized-bed reduction reactor 10. The reducing gas having gone through each of the fluidized-bed reduction reactors and that is then discharged from an upper side of the preheating reduction reactor 10a passes through a scrubber 92 for collecting dust by water and is then discharged.

As shown in FIG. 1, the apparatus for restoring fine iron 20 is connected to the final reduction reactor 1Od, thereby restoring and supplying the reduced fine iron that is reduced materials to the apparatus for manufacturing compacted iron 30 installed therebelow. The apparatus for manufacturing compacted iron 30 compacts the reduced materials for securing permeability of the melter-gasifier 40 and preventing scattering of dust. The apparatus for manufacturing compacted iron 30 includes a pair of rolls 301 and a compacted iron storage bin 303. The apparatus for manufacturing compacted iron 30 may further include other devices as necessary.

As shown in FIG. 1, the storage bin 60 is located between the apparatus for manufacturing compacted iron 30 and the melter-gasifier 40. The storage bin 60 reduces the compacted iron again by the reducing gas supplied from the melter-gasifier 40. Therefore, since re-reduced compacted iron is supplied to the melter-gasifier 40, a reduction load in the melter-gasifier 40 can be largely reduced.

A coal packed bed is formed in the melter-gasifier 40 by supplying lumped coal or coal briquettes thereto. The lumped coal or coal briquettes charged into the melter-gasifier 40 are gasified by a pyrolytic reaction in an upper portion of the coal packed bed and a combustion reaction by oxygen in a lower portion thereof. The reducing gas generated from the melter- gasifier 40 due to a gasification reaction is supplied to the fluidized-bed reduction reactor 10 through the reducing gas supply line 50 connected to a rear end of the final reduction rector 1Od. The reducing gas is used as a reduction agent and a fluidizing gas.

The cyclone 80 is connected to the melter-gasifier 40 through the reducing gas flow line 82, thereby collecting dust in the reducing gas that is discharged from the melter-gasifier 40. In this case, the cyclone 80 is connected to the reducing gas supply line 50, thereby supplying the reducing gas that is separated from the dust to the fluidized-bed reduction reactor 10 through the reducing gas supply line 50. The reducing gas is partly restored in the storage bin 60.

The dust collected in the cyclone 80 is temporarily restored in the dust storage bin 90 located below the cyclone 80 by gravity. The dust is injected by a dust spray device (not shown) installed below the dust storage bin 90 and is then recharged into the melter-gasifier 40. In this case, since the recharged dust is combusted and melted by the oxygen injected therewith, the dust is not re-scattered outside of the melter-gasifier 40. The fine particle injecting device 70 is connected to the reducing gas flow line 82 through the gas transferring line 72. The fine particle injecting device 70 transfers viscosity reducing materials through the gas transferring line 72 by using a gas pressure. The viscosity reducing materials transferred by a gas are injected to a direct upper side of the melter-gasifier 40. The injected viscosity reducing materials enter into the cyclone 80 after being moved along a gas stream of the reducing gas flow line 82. The viscosity reducing materials are mixed with the dust entering together with the reducing gas. Although a single injecting position is shown in FIG. 1, the number of gas transferring lines 72 correspond to that of the reducing gas flow lines 82 since a plurality of reducing gas flow lines 82 can be installed.

An amount of carbon in the reducing gas is raised or the viscosity reducing materials such as MgO powder, CaO powder, or SiO₂ powder can be added in order to reduce viscosity of the dust generated from the melter- gasifier 40.

Firstly, coke dry quenching (CDQ) dust is injected in order to raise the amount of carbon. Since the amount of carbon contained in the CDQ dust is 85% or more, the amount of carbon in the dust can be obtained to be about 40% or more if CDQ dust of 2 tons or more is injected per hour.

If the CDQ dust is used for raising the amount of carbon, viscosity of the dust becomes weaker as the amount of carbon increases. However, if the amount of the carbon becomes too high, a detrimental difference ratio between oxygen and carbon in the melter-gasifier 40 occurs. In addition, when the CDQ dust enters into the fluidized-bed reduction reactor 10, molding ability of the reduced materials can be deteriorated during compaction of the reduced materials. Therefore, the injecting amount of the CDQ dust is controlled to have an amount of carbon of not more than 60% in the dust.

Meanwhile, when the viscosity reducing materials except the CDQ dust are used, an effect of suppressing viscosity occurs when the amount of the viscosity reducing materials is not less than 2% of the total amount of generated dust. However, if the amount of the viscosity reducing materials is over 10wt% of the total amount of generated dust, slag that is generated in the melter-gasifier 40 may increase, basicity may be changed, and molding ability of the reduced materials during compaction thereof may be deteriorated. Therefore, the viscosity reducing materials are injected to be in a range from 2wt% to 10wt% of the total amount of generated dust.

FIG. 2 is a schematic inner cross-sectional view magnifying a portion II of FIG. 1. FIG. 2 schematically shows a state in which the viscosity of the dust is reduced by the viscosity reducing materials. As shown in FIG. 2, the viscosity reducing materials 100 enter into the reducing gas flow line 82 through the gas transferring line 72. Therefore, the dust 200 sticks to the viscosity reducing materials 100 due to the viscosity of the viscosity reducing materials 100. Since the dust 200 entering into the fluidized-bed reduction reactor 10

(shown in FIG. 1, the same hereinafter) is a state of sticking to the viscosity reducing materials 100, it does not stick to the nozzles of the distribution plate or the cyclone but passes therethrough as is. As described above, the viscosity reducing materials 100 are injected, and thereby a possibility that the dust 200 sticks to the fluidized-bed reduction reactor 10 is lowered. That is, the viscosity problem of the dust 200 is reduced.

In this case, when the sticky dust 200 and the viscosity reducing materials 100 in the reducing gas are not uniformly mixed together, the viscosity problem of the total dust 200 is not reduced due to a partial segregation of the injected materials. Therefore, the viscosity reducing materials 100 are injected to a position that is as far as possible from the cyclone 80 in order for the viscosity reducing materials 100 to be sufficiently mixed with the sticky dust 200 in the reducing gas flow line 82. That is, the viscosity reducing materials 100 are injected to a position that is as close as possible to the melter-gasifier 40.

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

WHAT IS CALIMED IS

1. An apparatus for manufacturing molten iron, the apparatus comprising: at least one fluidized-bed reduction reactor that reduces and plasticizes fine iron; an apparatus for manufacturing compacted iron that molds the fine iron and manufactures compacted iron; a melter-gasifier into which the compacted iron is charged and oxygen is injected, the melter-gasifier manufacturing molten iron; a reducing gas supply line that supplies reducing gas discharged from the melter-gasifier to the fluidized-bed reduction reactor; and a fine particle injecting device that injects viscosity reducing materials into the reducing gas such that viscosity of dust contained in the reducing gas is reduced.

2. The apparatus of Claim 1, further comprising: a reducing gas flow line that is connected to an upper side of the melter- gasifier; and a cyclone to which the reducing gas is supplied from the reducing gas flow line connected thereto, the cyclone collecting dust in the reducing gas.

3. The apparatus of Claim 2, further comprising a dust storage bin that is connected to a lower side of the cyclone and that restores the dust collected in the cyclone and recharges the dust into the melter-gasifier.

4. The apparatus of Claim 2, wherein the fine particle injecting device is connected to the reducing gas flow line by a gas transferring line that transfers the viscosity reducing materials to the reducing gas supply line by a gas.

5. The apparatus of Claim 4, wherein the gas transferring line is connected to the reducing gas flow line at a position that is closer to the melter- gasifier than the cyclone.

6. The apparatus of Claim 1, wherein the viscosity reducing materials are coke dry quenching (CDQ) dust.

7. The apparatus of Claim 1, wherein the viscosity reducing materials are MgO powder, CaO powder, or Siθ2 powder.

8. A method for manufacturing molten iron, the method comprising: reducing and plasticizing fine iron in a fluidized-bed reduction reactor; compacting the reduced and plasticized fine iron; charging the compacted fine iron into a melter-gasifier; supplying a reducing gas generated from the melter-gasifier to the fluidized-bed reduction reactor; and lowering viscosity of the dust in the reducing gas by supplying viscosity reducing materials to the reducing gas.

9. The method of Claim 8, further comprising collecting the dust in the reducing gas generated from the fluidized-bed reduction reactor by using a cyclone.

10. The method of Claim 9, further comprising restoring the collected dust and recharging the collected dust into the melter-gasifier.

11. The method of Claim 9, wherein the viscosity reducing materials are injected between the melter-gasifier and the cyclone.

12. The method of Claim 11, wherein the viscosity reducing materials are injected at a position that is closer to the melter-gasifier than the cyclone.

13. The method of Claim 8, wherein the viscosity reducing materials are coke dry quenching (CDQ) dust.

14. The method of Claim 13, wherein the coke dry quenching (CDQ) dust is injected into the reducing gas such that an amount of carbon contained in the dust is not more than 60%.

15. The method of Claim 8, wherein the viscosity reducing materials are MgO powder, CaO powder, or Siθ2 powder.

16. The method of Claim 15, wherein the viscosity reducing materials are injected to be in a range from 2wt% to 10wt% of the dust.