TITLE OF THE INVENTION
METHOD AND APPARATUS FOR MANUFACTURING MOLTEN IRON
CROSS-REFERENCE TO RELATED APPLICATION
5 This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0160637 filed in the Korean Intellectual Property Office on December 20, 2014, the entire contents of which are incorporated herein by
reference.
10 BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a technology for manufactuhng molten iron.In more detail, the present invention relates to a method and an apparatus for manufacturing molten iron which Improve bad tapping due to deterioration of
15 fluidity of slag in a melting furnace.
(b) Description of the Related Art
Recently,in order to solve problems of blast furnaces, iron-manufacturing companies of countries around the world have made large
efforts to develop a smelting reduction process of manufacturing molten iron by
20 directly using common coal as a fuel and a reducer and directly using a fine ore,
which makes up 80 % of the world ore production volume, as an iron source.
The smelting reduction process of manufacturing molten iron by directly using a fine ore includes a reduction process of reducing a fine ore and a melting process of melting the reduced fine ore in a melting furnace. As smelting reduction equipment, FINEX equipment and COREX equipment have been known in accordance with the reduction process.
The FINEX equipment includes a multi-step fluidized reduction furnace and hot-compacting equipment, and a melter-gasifier (hereafter referred to as a
5 melting furnace) connected to them. A fine ore and sub-raw matenals at room temperature are sequentially reduced through a plurality of fluidized reduction furnaces. The reduced iron is hot-compacted into compacted iron through the
hot-compacting equipment and then fed into the melting furnace. The melting furnace manufactures molten iron by melting the reduced iron ore. A large amount of carbon monoxide is produced in the melting furnace due to combustion of coal and is put into the fluidized reduction furnace as a reduction gas.
The COREX equipment includes a reduction furnace and a melting furnace. Main raw materials such as iron ore and pellets including lump ore and fine ore as well as sub-raw materials such as limestone and dolomite are put into the reduction furnace and reduced therein. The melting furnace manufactures molten iron by melting the reduced iron ore. The carbon monoxide produced in combustion by oxygen taken in the melting furnace through a tuyere and the reduction gas of which the main component is hydrogen are put into the reduction furnace.n the melting furnace, the reduction iron and the sub-raw materials are melted into pig iron and slag by high-temperature heat generated by combustion of coal that is the main raw material.The slag interferes with the pig iron
coming out through an iron notch of the melting furnace, when its fluidity decreases in the melting furnace.The critical factors determining fluidity of the slag are silicon dioxide (Si02), aluminum oxide (AI2O3), calcium oxide (CaO), and magnesium oxide (MgO), and when the composition ratio of them is poor, the fluidity of the slag
decreases. Further, when the temperature of the pig iron drops under 1450 °C due to
poor control of furnace heat, the temperature to the melting point of the slag is
low, so the fluidity decreases.
Accordingly, in the related art, there were an effort for minimizing the
10 composition ratio of silicon dioxide (Si02), aluminum oxide (AI2O3), calcium oxide
(CaO), and magnesium oxide (MgO) by adjusting the feeding amount of ore,
coal, and sub-raw materials and an effort for preventing a decrease in fluidity of
slag by adjusting the melting point of the slag by controlling pig iron temperature.
However, it is very difficult to feed the exact amount of silicon dioxide
15 (Si02), aluminum oxide (AI2O3), calcium oxide (CaO), and magnesium oxide
(MgO) at the composition ratio, and it is also difficult to accurately control the pig
iron temperature.
The above information disclosed in this Background section is only for
enhancement of understanding of the background of the invention and therefore
20 it may contain information that does not form the prior art that is already known
in this country to a person of ordinary skill in the art.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to provide a method
and an apparatus for manufacturing molten iron having advantages of improving bad tapping from a melting furnace by improving fluidity of slag in the melting furnace.
The present invention has also been made in an effort to provide a method and an apparatus for manufacturing molten iron which can more easily Nincrease fluidity of slag.The method of the present exemplary embodiment may be capable of
ncreasing fluidity of slag by decreasing the melting point of the slag. The method of manufacturing molten metal may include adding powder for decreasing the molting point of slag into a melting furnace through a tuyere of the melting furnace. The powder may be put into the tuyere of the melting furnace together
with pulverized coal, when the pulverized coal is put in. To this end, the adding of powder into the furnace may include delivering the powder stored in a powder bin, putting the delivered powder into the pulvenzed coal bin holding pulverized coal, mixing the pulverized coal with the powder, and feeding the pulverized coal mixed with the powder to the tuyere of the melting furnace. The addition amount of the powder may be set to 0.5 to 1 wt% of the amount of slag produced in the melting furnace.
20 The apparatus for manufactuhng molten iron of the present exemplary
embodiment may include a powder feeder for adding powder for decreasing the
melting point of slag into a tuyere of the melting furnace.
The apparatus for manufacturing molten iron may further include a pulverized coal feeding line connected to the tuyere of the melting furnace and a pulverized coal bin connected with the pulverized coal feeding line and supplying
pulverized coal, and the powder feeder may be connected to the pulverized coa
bin and may supply powder into the pulverized coal bin.
The powder feeder may include a powder bin holding powder, a delivery line connected between the lower portion of the powder bin and the pulverized coal bin to deliver powder, and a gas supplier connected to the delivery line and
supplying a delivery gas for delivering the powder.
The powder may include an alkali material. The powder may be light
soda ash (Na2C03).
10 According to the present exemplary embodiment, since the melting point
of slag is decreased by adding light soda ash thereto, fluidity of slag can be
ncreased. Accordingly, it is possible to solve the problem of bad tapping from
a melting furnace due to a decrease in fluidity of slag and to achieve smoother
tapping.
lb Since light soda ash is put into a melting furnace together with pulverized
coal, work is facilitated and fluidity of slag can be more simply increased.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram illustrating an apparatus for manufacturing
molten iron according to the present exemplary embodiment
20 FIG. 2 is a schematic flowchart illustrating a process of manufacturing
molten iron according to the present exemplary embodiment
DETAILED DESCRIPTION OF THE EMBODIMENTS
Hereinafter, exemplary embodiments of the present invention will be
described in detail with reference to the accompanying drawings so that those
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skilled in the art can easily achieve the present invention. As is understood by
those skilled in the art, the following exemplary embodiments may be modified in
vahous ways without departing from the concept and scope of the present invention. Like reference numerals are used for like components in the

5

drawings.

The terminologies used hereafter are only for describing a specific exemplary embodiment and not intended to limit the present invention. The
singular terms used herein include plural terms unless phrases clearly express
opposite meanings. The term 'including' used herein refers to concrete specific
10 characteristics, regions, positive numbers, steps, operations, elements, and/or
components, not limiting the existence or addition of other specific
characteristics, regions, positive numbers, steps, operations, elements, and/or
components.
All the terms, including technical terms and scientific terms used
15 hereafter, have the same meanings as those that those skilled in the art
generally understand. The terms defined in dictionaries should be construed
as having meanings corresponding to the related prior art documents and those
stated herein, and not be construed as being ideal or official, if not otherwise
defined.
20 FIG. 1 is a schematic diagram illustrating an apparatus for manufacturing
molten iron according to the present exemplary embodiment.
As illustrated in FIG. 1, an apparatus for manufacturing molten iron
manufactures molten iron using an iron-containing material and coal. The
apparatus for manufacturing molten iron includes a melting furnace 100 that
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manufactures molten iron, using reduced iron that is reduced through one or
more fluidized bed-type reduction furnaces for manufacturing fine reduced iron by reducing fine ore or reduced iron through a packed bed type of reduction furnace for reducing iron-containing matehals such as coarse-grained iron ore

t)

and pellets of which the grain size is 8 mm or more in addition to fine ore.

The reduced iron is fed into the melting iron 100 and melted into molten
iron by combustion of a coal-filled layer formed by an agglomerated
carbonaceous material. An agglomerated carbonaceous material that is fuel
and compacted iron obtained by hot-compacting reduced iron are sequentially
10 supplied into the melting furnace 100 and oxygen is fed into the melting furnace
through a tuyere 102 on the outer wall, thereby burning coal. The combustion
gas of the coal changes into a high-temperature reduction flow while hsing in the
melting furnace 100. The reduction gas discharged from the melting furnace
100 is delivered to a cyclone through a discharge pipe connected to a gas
15 discharge hole and then supplied to a reduction furnace through the cyclone.
The apparatus for manufacturing molten iron further includes pulverized
coal feeding equipment 200 for feeding pulverized coal through the tuyere 102 of
the melting furnace 100. The pulverized coal is used for stabilizing work with a
melting furnace and reducing fuel by controlling the combustion temperature.
20 The pulverized coal feeding equipment 200 supplies pulverized coal as
the sub-fuel and oxygen to the tuyere 102 of the melting furnace 100. The
pulverized coal feeding equipment 200 includes a grinding mill 202 for crushing
coal into powder, a back filter 204 that sorts the pulverized coal crushed by the
grinding mill 202 in accordance with the grain size, a pulverized coal bin 206 that
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stores the pulverized coal passing through the back filter 204, and a pulverized
coal feeding line 208 for supplying the pulverized coal stored in the pulverized
coal bin 206 to the tuyere 102 of the melting furnace 100.
The pulverized coal formed by the grinding mill 202 is stored in the

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pulverized coal bin 206 after passing through the back filter 204, and is then

supplied to the tuyere 102 of the melting furnace 100 through the pulvehzed coa
feeding line 208. The pulverized coal fed into the melting furnace 100 together
with oxygen through the tuyere 102 melts the reduced iron as the sub-fuel.
The apparatus for manufacturing molten iron further includes a powder
10 feeder 300 for adding powder for decreasing the melting point of slag into the
melting furnace 100 through the tuyere 102 of the melting furnace 100
n the present exemplary embodiment, the powder may include light
soda ash (Na2C03). The light soda ash is put into the melting furnace 100 and
decreases the melting point of the slag by increasing Na20 in the slag.
15 Accordingly, the melting point of the slag decreases and fluidity of the slag
increases
n general, the fluidity of the slag depends on viscosity, basicity, and
melting temperature. When the melting point of the slag decreases, the fluidity
is improved, so the slag easily reacts in the melting furnace 100, and its specific
20 gravity is lower than that of pig iron so it floats over the pig iron and is easily
separated.
The powder feeder 300 is connected to the pulverized coal bin 206, and
puts powder with pulverized coal into the melting furnace 100 by supplying
powder into the pulverized coal bin 206.
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To this end, the powder feeder 300 includes a powder bin 302 that stores
powder, a delivery line 304 that is connected between the lower portion of the
powder bin 302 and the pulverized coal bin 206 to deliver the powder, and a gas supplier 306 that is connected to the delivery line 304 and supplies a delivery

o

gas for delivering powder.

The powder bin 302, which is a container holding powder therein, has an
exit at the bottom through which the powder is discharged. The exit of the
powder bin 302 is connected with the delivery line 304. The powder feeder 300
delivers the powder using a gas. An end of the delivery line 304 is connected
10 with the gas supplier 306 to be supplied with the powder delivery gas, and the
other end is connected to the pulverized coal bin 206. Accordingly, the powder
in the powder bin 302 is discharged to the delivery line 304 through the exit and
delivered into the pulverized coal bin 206 by the gas flowing through the delivery
ine 304.
15 The gas supplier 306 supplies an inert gas to the delivery line 304 to
deliver the powder. In the present exemplary embodiment, the gas supplied
from the gas supplier 306 may be nitrogen (N2).
The term 'powder' used herein means particles with a small grain size.
n the present exemplary embodiment, since the powder is put into the melting
20 furnace together with the pulverized coal, it may have a size and density
corresponding to those of the pulverized coal. The pulverized coal is managed
such that the ratio of grains of 70 ^im is about 90 wt% or more, so the powder is
also managed in the same way. When the grain size of the powder is larger
than the grain size of the pulverized coal, reaction ability in a melting furnace
9

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decreases, but when it is too small, delivery ability decreases.
The powder supplied into the pulverized coal bin 206 is mixed with pulverized coal and put into the melting furnace 100 through the tuyere 102 of the melting furnace 100. The powder and the pulverized coal may be mixed in the pulverized coal bin 206. As stated above, the powder and the pulverized
coal are similar in grain size and specific gravity, so they are easily mixed in the pulverized coal bin. That is, pulverized coal and powder are put into the pulverized coal bin through separate inlets and are naturally mixed during

settling of the pulverized coal bin.
10 The powder put in the melting furnace 100, as stated above, increases
fluidity of the slag by decreasing the melting point of the slag. Accordingly, it is
possible to prevent bad tapping due to the slag when tapping through a tap
notch 104 of the melting furnace 100.
Hereinafter, a process of manufactuhng molten iron of the present
15 exemplary embodiment is described with reference to FIG. 2.
First, describing a process of manufacturing molten iron by means of the
melting furnace 100, reduced iron reduced through a reduction furnace and coa
that is a fuel are fed into the melting furnace 100. Oxygen and pulvehzed coa
are fed through the tuyere 102 of the melting furnace 100, so the coal is burned
20 and the reduced iron is melted by the combustion heat. Pig iron and slag
produced in the melting furnace 100 are separated due to the difference in
specific gravity, and the pig iron is taken out through the iron notch 104 formed
at the lower portion of the melting furnace 100.
n this process, the method of manufacturing molten iron according to the
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present exemplary embodiment increases fluidity of the slag by decreasing the
melting point of the slag, so smooth tapping can be performed
As illustrated in FIG. 2, the method of the present invention further
includes putting powder for decreasing the melting point of slag into the melting

^)

furnace in the process of feeding oxygen and pulverized coal through the tuyere

of the melting furnace.
n the present exemplary embodiment, the powder is put into the melting
furnace through the tuyere, similar to the pulverized coal.
To this end, the putting of powder into the furnace includes delivering the
10 powder stored in the powder bin (S100), putting the delivered powder into the
pulverized coal bin holding pulverized coal (S120), mixing the pulverized coa
with the powder (S140), and feeding the pulverized coal mixed with the powder
to the tuyere of the melting furnace (S160).
The powder stored in the powder bin through the process described 15 above is supplied to the pulverized coal bin and mixed therein, and then it is put
into the melting furnace together with the pulverized coal when the pulverized
coal is fed into the melting furnace.
The powder may be an alkali material. As the alkali material, an alkali
material in which a hazardous substance such as chlorine (CI) is not included
20 may be used.
n the present exemplary embodiment, the powder is light soda ash
(Na2C03).
The light soda ash put in the melting furnace produces Na20 in
accordance with the following Reaction Formula 1.
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Na2C03 -> Na20 + CO2 Reaction Formula 1
When an alkali substance such as Na is mixed with slag, the melting
point of the slag decreases. The NaaCOa fed in the melting furnace is thermally
decomposed into Na20 and CO2. That is, Na20 that is an alkali substance

0

assists the slag to be easily dissolved by breaking chain links of Si02.

Accordingly, Na20 of the components of the slag increases in the melting
furnace, so the melting point of the slag decreases. As the melting point of the
slag decreases, the fluidity of the slag increases.
Accordingly, the pig iron and the slag are separated well, and bad 10 tapping due to the slag when the pig iron is tapped can be minimized.
In the present exemplary embodiment, the addition amount of light soda
ash that is a powder can be set within a range of 0.5 to 1 wt% of the anticipated
production amount of slag produced in the melting furnace. As a test result, it
was found that when light soda ash was added within the range, the melting
lb point of the slag decreased by 30 to 40'C degrees. Accordingly, it is possible
to solve the problem of blocking the iron notch when tapping from a melting
furnace. When light soda ash is added out of the range, the efficiency of the
addition amount decreases and the amount of alkali circulating in the furnace
increases, so it may cause a problem with the equipment such as pipes.
20 As described above, it is possible to increase fluidity of slag and achieve
smooth tapping by adding light soda ash into a melting furnace.
While this invention has been described in connection with what is
presently considered to be practical exemplary embodiments, it is to be
understood that the invention is not limited to the disclosed embodiments, but,
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on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

100 : Melting furnace

102 : Tuyere

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104 : Iron notch

200 : Pulverized coal feeding equipment

202 : Grinding mill

204: Back filter

206 : Pulverized coal bin

208 : Feeding line

300 : Powder feeder

302: Powder bin

WE CLAIM:-
1. A method of manufacturing molten iron using an apparatus for
manufacturing molten iron including a reduction furnace for manufacturing
5 reduced iron by reducing an iron-containing material and a melting furnace for
manufacturing molten iron by melting reduced iron
increases fluidity of slag by comprising adding powder for decreasing the
melting point of slag into the melting furnace through a tuyere of the melting
furnace.
10
2. The method of claim 1, wherein the powder is added together
with pulverized coal when the pulverized coal is put into the tuyere of the melting
furnace.
15 3. The method of claim 2, wherein the addition of powder into the
furnace includes: delivering the powder from a powder bin holding the powder;
adding the delivered powder to a pulverized coal bin holding pulverized coal;
mixing the pulverized coal with the powder; and feeding the pulverized coa
mixed with the powder into the tuyere of the melting furnace.
20
4. The method of claim 1, wherein the powder is an alkali material.
5. The method of any one of claims 1 to 4, wherein the powder is
ight soda ash (Na2C03).
14

6. The method of claim 5, wherein the addition amount of the
powder is 0.5 to 1 wt% of the amount of slag produced in the melting furnace
5 7. An apparatus for manufacturing molten iron which includes a
reduction furnace for manufacturing reduced iron by reducing an iron-containing
material and a melting furnace for manufacturing molten iron by melting reduced
iron, the apparatus comprising
a powder feeder for adding powder for decreasing the melting point of
10 slag into a tuyere of the melting furnace.
8. The apparatus of claim 7, further comprising a pulverized coal
feeding line connected to the tuyere of the melting furnace and a pulverized coa
bin connected with the pulverized coal bin and supplying pulverized coal,
15 wherein the powder feeder is connected to the pulverized coal bin and
supplies powder into the pulverized coal bin.
9. The apparatus of claim 8, wherein the powder feeder includes a
powder bin holding powder, a delivery line connected between the lower portion 20 of the powder bin and the pulverized coal bin to deliver powder, and a gas
supplier connected to the delivery line and supplying a delivery gas for delivering
the powder.
10. The apparatus of claim 9, wherein the powder is light soda ash
15

(NazCOa).