Title of Invention

A METHOD AND APPARATUS FOR MANUFACTURING MOLTEN IRON

Abstract Provided is an apparatus for manufacturing molten iron using directly fine or lump coals and fine iron-containing ores, a method thereof, an integrated steel mill using the same, and a method thereof. The method of manufacturing the molten iron comprises the steps of : manufacturing iron-containing mixture by mixing fine iron- containing ores and supplementary raw materials and by drying the resultant mixture, converting the iron-containing mixture to a reduced material by reducing and sintering while passing the iron-containing mixture through multi-stage fluidized-bed reactor unit, which are sequentially connected to each other, manufacturing briquettes by briquetting the reduced material at high temperature, forming a coal packed bed by charging lump coals and briquettes which are made by briquetting fine coals, into a melter-gasifier as heat sources for melting the briquettes, manufacturing molten iron by charging the briquettes into the melter-gasifier connected to the multi-stage fuidized-bed reactor unit and by supplying oxygen into the melter-gasifier, and supplying reducing coal-gas exhausted from the melter- gasifier into the multi-stage fluidized-bed reactor unit.
Full Text A METHOD AND APPARATUS FOR MANUFACTURING MOLTEN IRON
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to an apparatus for manufacturing molten iron,
a method thereof, an integrated steel mill using the same, and a method thereof,
and more particularly, to an apparatus for manufacturing molten iron directly using
fine or lump coals and fine iron-containing ores, a method thereof, an Integrated
steel mill using the same, and a method thereof.
(b) Description of the Related Art
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, etc. Further, it is an industry which has advanced since the dawn of
human history. Iron works, which play a pivotal roll in the iron and steel industry,
produce steel from the molten iron, and then supply it to customers after producing
molten iron (i.e., Pig iron in a molten state) using iron ores and coals as raw
materials.
Nowadays, approximately 60% of the world's iron production is produced
using the blast furnace method that has been developed since the 14th century.
According to the blastfurnace method, coke produced using iron ore and bituminous
coal as raw materials that went through a sintering process, are placed in a blast
furnace and oxygen is supplied to the furnace to reduce the iron ore to iron, thereby
manufacturing molten iron. The blast furnace method which most of molten iron
production employ requires that raw materials have a hardness of at least a
predetermined level and grain size that can ensure ventilation property in the
furnace, taking into account reaction characteristics. For that reason, coke that is
obtained by processing specific raw coal is needed as a carbon source to be used
as fuel and a reducing agent. Also, sintered ore that went through a successive
agglomerating process Is needed as an iron source. Accordingly, the modern blast
furnace method requires raw material preliminary processing equipment such as
coke manufacturing equipment and sintering equipment. Furthermore, it is
necessary to be equipped with subsidiary facility, in addition to the blast furnace,
and equipments for preventing and minimizing pollution generated by subsidiary
facilities. Therefore, the heavy investment in additional facilities and equipments
leads to increasing manufacturing costs.
In order to solve these problems with the blast furnace method, significant
effort is made in iron works all over the world to develop a smelting reduction
process that produces molten iron by using directly fine coals, as fuel and a
reducing agent, and using as iron sources, directly fine ores which account for more
than 80% of the world's ore production.
As an example of such a smelting reduction process, a method of
manufacturing the molten iron using fine iron ores and lump coals is disclosed in US

Patent No. 5,534,064. Here, the whole apparatus is comprised of a multi-stage
fluidized-bed type reactor and a packed bed type melter-gasifier that is connected to
a final stage of the multi-stage fluidized-bed reactor unit, such that fine iron-source
can be directly used due to a characteristic of the fluidized-bed of the fluidized-bed
type reactor unit. However, since it is necessary to secure a predetermined space
inside the packed bed of the melter-gasifier, a range of grain size of coals, which are
directly input into the melter-gasifier, is limited. Further, the fine coal source
reduced in the multi-stage fluidized-bed reactor unit has to be continuously input into
the melter-gasifier. So, there is a need for a special charging method. Specifically,
since a permissible range of grain size of coal, which is used as fuel and a reducing
agent, is limited, a significant amount of fine coals which are generated during coal
mining, transportation, and open-air storage cannot be used. Further, in the
process of operating a packed bed type reactor unit, a significant amount of fine iron
source cannot be used as an iron source. Furthermore, in the process of operating
a fluidized-bed type reactor unit, it is needed to provide additional apparatus for
continuously charging fine reduced iron discharged from the fluidized-bed type
reactor unit into the melter-gasifier.
US Patent No. 5,961,690 discloses a method of manufacturing the whole
product of molten pig iron or molten steel and a plant for implementing the method.
Here, an apparatus for manufacturing molten iron by connecting a multi-stage
fluldizing-bed reactor unit and a melter-gasifier while preventing sticking and a
method thereof are disclosed. Here, part of reducing gas flow, which flows from a
final reactor to a pre-reducing reactor, is divided, and is cooled to a room
temperature and compressed. Then, the divided reducing gas is re-supplied to the
final reactor after removing CO2 contained in the divided reducing gas in order to
increase an amount of the reducing gas and thereby reduce iron ore. At this time,
a temperature of the gas to be supplied to a final reactor is raised by an additional
heater to a predetermined temperature before it is supplied to the final reactor,
thereby keeping a temperature inside the final reactor.
Further, as a method of raising a temperature of room-temperature-
reducing gas, a heat-exchanging scheme in which a temperature is raised by
contact with high-temperature gas additionally supplied or a self temperature-raising
scheme is considered. In the self temperature-raising scheme, part of room-
temperature-reducing gas is combusted and combustion heat thereof is used to
raise the temperature of the reducing gas. However, in the heat-exchange scheme,
additional gas is needed to generate high-temperature gas. In the self
temperature-raising scheme, an amount of reducing gas components such as CO,
H2, etc. existing In the reducing gas to be supplied to the final reactor decreases due
to the combustion of part of the room-temperature gas. Further, in both of the
schemes, the temperature of room-temperature gas has to be directly raised, such
that a heat efficiency decreases during the time of raising the temperature, thereby
increasing an amount of energy consumption during the process.
In the US Patent No. 5,961,690, a method of cooling down exhaust gas
from the melter-gasifier to a temperature suitable for its supply to the final reactor is
also disclosed. In the method, part of the reducing gas which is to be re-supplied
to the final reactor is divided before being heated and then mixed with the exhaust
gas from the melter-gasifier.
On the other hand, tar and dust, which are generated by heating coals and
removing volatile matters therefrom at the upper portion of the melter-gasifier during
a practical operation, sequentially pass through the multi-stage fluidized-bed reactor
unit, along with the reducing gas discharged from the melter-gasifier. In this case,
the tar is gradually pyrolyzed in the reducing gas and disappears. The dust is
introduced into fine ore flow sequentially passing through the multi-stage fluidized-
bed reactor unit while traversing the reducing gas in each of the reactors and is
again circulated into the melter-gasifier. Therefore, amounts of dust and tar
contained in the reducing gas decreases while they pass through the multi-stage
fluidized-bed reactor unit
However, in the apparatus and the method disclosed in the US Patent No.
5,961,690, since the reducing gas flow divided from the final reactor passes through
only one fluidized-bed, the reducing gas contains a large amount of tar and dust.
Therefore, during the process of cooling down the divided reducing gas and of
removing CO2 therefrom and compressing it, tar contained in the reducing gas
condenses on devices provided as apparatus for cooling the reducing gas and for
removing CO2 and condensing it, which leads to making mechanical trouble during
operation. Further, in the apparatus and the method disclosed in the US Patent No.
5,961,690, since there is needed to provide a cooling apparatus using water for
cooling down the divided high-temperature reducing gas in addition to a cooling
apparatus using water for cooling down gas which is finally discharged from the
multi-stage fluidized-bed reactor unit, whereby an amount of used cooling water is
increased and load is excessively applied to all the processes.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above-mentioned
problems, and an object of the invention is to provide an apparatus for
manufacturing molten iron which uses fine or lump coals and fine iron-containing
ores and which can excellently keep a reduction ratio of iron-containing ores during
the time of gas-reducing iron-containing ores using reducing coal gas generated
from coal, and a manufacturing method thereof.
Further, another object of the invention is to provide an integrated steel mill
using the above-described apparatus for manufacturing molten iron and the method
thereof, and a method thereof, thereby providing hot-rolled steel plate having an
excellent quality while compactly installing all the apparatuses and processes.
According to an aspect of the invention to achieve the above-mentioned
object, there is provided a method of manufacturing molten iron, comprising the
steps of: manufacturing iron-containing mixture by mixing fine iron-containing ores
and supplementary raw materials and by drying the resultant mixture; converting the
iron-containing mixture to a reduced material by reducing and sintering while
passing the iron-containing mixture through a multi-stage fluidized-bed reactor unit,
of which reactors are sequentially connected to each other; manufacturing
briquettes by briquetting the reduced material at high temperature; forming a coal
packed bed by charging lump coals and briquettes which are made by briquetting
fine coals, into a melter-gasifier as heat sources for melting the briquettes;
manufacturing molten iron by charging the briquettes into the melter-gasifier
connected to the multi-stage fluidized-bed reactor unit and by supplying oxygen into
the melter-gasifier; and supplying reducing coal-gas exhausted from the melter-
gasifier into the fluidized-bed reactor unit.
Further, the method of manufacturing molten iron may further comprise the
steps of: dividing the exhaust gas flow which is exhausted through the multi-stage
fluidized-bed reactor unit and removing CO2 from the exhaust gas; mixing the
reformed exhaust gas from which CO2 is removed with the reducing coal gas which
is exhausted from the melter-gasifier, and heating the reducing coal gas mixed with
the reformed exhaust gas before supplying it to the multi-stage fluidized-bed reactor
unit to adjust a temperature of the reducing coal gas to a temperature required to
reduce the iron-containing mixture at the multi-stage fluidized-bed reactor unit
The reformed exhaust gas may be heated using an oxygen burner at the
heating step before supplying the reducing coal gas mixed with the reformed
exhaust gas to the multi-stage fluidized-bed reactor unit
In the step of dividing the exhaust gas flow which is exhausted through the
multi-stage fluidized-bed reactor unit and removing CO2 from the exhaust gas, an
amount of divided exhaust gas is preferably 60 volume% of a total amount of the
exhaust gas which is exhausted from the multi-stage fluidized-red reactor unit.
The amount of the reformed exhaust gas may be maintained at a range of
1050 Nm3 to 1400 Nm3 per 1 ton of the fine iron-containing ores.
In the step of mixing the reformed exhaust gas from which CO2 is removed
with the reducing coal gas exhausted from the melter-gasifier, it is preferable that an
amount of CO2 contained in the reformed exhaust gas is 3.0 volume% or less.
The divided exhaust gas may be compressed at the step of dividing the
exhaust gas flow exhausted from the multi-stage fluidized-bed reactor unit and
removing CO2from the exhaust gas.
It is preferable to further comprise a step of dividing the exhaust gas flow
which is exhausted through the multi-stage fluidized-bed reactor unit and removing
tar from the exhaust gas, before the step of dividing the exhaust gas flow which is
exhausted from the multi-stage fluidized-bed reactor unit and removing CO2 from the
exhaust gas.
In the step of mixing the reformed exhaust gas from which CO2 is removed
with the reducing coal gas which is exhausted from the melter-gasifier, the reformed
exhaust gas is mixed at a front end of a cyclone which charges dust exhausted from
the melter-gasifier into the melter-gasifier.
The reformed exhaust gas flow from which CO2 is removed may be divided
and used as carrier gas for charging dust separated at the cyclone into the melter-
gasifier.
The method of manufacturing molten iron according to the present
invention, may further comprises a step of bypassing a total amount of exhaust gas
which is exhausted from the multi-stage fluidized-bed reactor unit and supplying it to
the multi-stage fluidized-bed reactor unit during the time of closing the melter-
gasifier or before operating the melter-gasifier.
The method of manufacturing molten iron according to the present
invention, may further comprises the steps of: dividing the exhaust gas flow which is
exhausted through the multi-stage fluidized-bed reactor unit and removing CO2 from
the exhaust gas flow; and purging the multi-stage fluidized-bed reactor unit by
dividing the reformed exhaust gas flow from which CO2 is removed and by supplying
the reformed exhaust gas to each of the fluidized-bed reactors.
It is preferable that an amount of nitrogen contained in the reducing coal
gas is 10.0 volume% or less.
The method of manufacturing molten iron according to the present
invention, may further comprises the steps of: dividing the exhaust gas flow which is
exhausted through the multi-stage fluidized-bed reactor unit and removing CO2
contained in the exhaust gas; and dividing the reformed exhaust gas flow from
which CO2 is removed and supplying it into the melter-gasifier together with oxygen
during the time of supplying oxygen to the melter-gasifier.
The step of converting the iron-containing mixture to a reduced material
may comprise: a first step of preheating the iron-containing mixture at a temperature
of 400 to 500°C; a second step of re-preheating the preheated iron-containing
mixture at a temperature of 600 to 700°C; a third step of pre-reducing the re-
preheated iron-containing mixture at a temperature of 700 to 800°C; and a fourth
step of finally reducing the pre-reduced iron-containing mixture at a temperature of
770 to 850°C.
A degree of oxidation at the first and second steps may be 25% or less, a
degree of oxidation at third step may be 35 to 50%, and a degree of oxidation at
fourth step may be 45% or more. Here, the degree of oxidation is obtained by a
following equation: (CO2 volume% + H2O volume%)/(CO volume% + H2 volume% +
CO2 volume% + H20 volume%) x 100; CO, CO2, H2O and H2 are gases, each of
which is contained in the reducing gas.
The second and third steps may comprise a step of supplying oxygen.
In the step of manufacturing the briquettes at a high temperature, it is
preferable that the grain size of the briquettes is within a range of 3 mm to 30 mm.
In the step of forming the coal packed bed, It is preferable that the grain
size of the briquette Is within a range of 30 mm to 50 mm.
An integrated steel manufacturing method according to the present
invention comprises the steps of: manufacturing molten iron by the above-
mentioned method of manufacturing molten iron; manufacturing molten steel by
removing impurities and carbon contained in the molten iron; continuously casting
the molten iron into thin slab; hot-rolling the thin slab to make hot-rolled steel plate.
In the step of continuously casting the molten iron into the thin slab, the
molten steel may be continuously cast into the thin slab having a thickness of 40
mm to 100 mm.
In the step of hot-rolling the thin slab to make hot-rolled steel plate, the hot-
rolled steel plate may have a thickness of 0.8 mm to 2.0 mm.
The step of manufacturing the molten steel may comprise the steps of: pre-
treating the molten iron to remove phosphorus and sulfur contained in the molten
iron; removing carbon and impurities contained in the molten iron by supplying
oxygen into the molten iron; and manufacturing the molten steel by removing
impurities and dissolved gas by way of secondary refining of the molten iron.
The integrated steel manufacturing method may further comprise the steps
of: converting fine iron-containing ores to reduced Iron by reducing the fine iron-
containing ores while passing it through a multi-stage fluidized-bed reactor unit, of
which reactors are sequentially connected to each other; and manufacturing
reduced-iron briquettes by briquetting the reduced iron at a high temperature. In
the step of removing carbon and impurities contained in the molten iron, the
reduced-iron briquettes and the molten iron may be mixed, and carbon and
impurities be removed therefrom.
The step of converting the fine iron-containing ores to the reduced iron may
comprise the steps of: preheating the fine iron-containing ores at a temperature of
600 to 700°C; pre-redudng the preheated fine iron-containing ores at a temperature
of 700 to 800°C; and final-reducing the pre-reduced fine iron-containing ores at a
temperature of 770 to 850°C to convert it to reduced iron.
An apparatus for manufacturing molten iron according to the present
invention comprises: a multi-stage fluidized-bed reactor unit for converting fine iron-
containing ores which are mixed and dried and supplementary raw material to a
reduced material; an briquette-manufacturing apparatus which is connected to the
multi-stage fluidized-bed reactor unit and which manufactures briquettes by
briquetting the reduced material at a high temperature; a briquetter for
manufacturing briquettes which are used as a heat source by briquetting fine coals;
a melter-gasifier for manufacturing molten steel, into which lump coals and the
briquettes manufactured from the briquetter are input and a coal packed bed is
formed, into which the reduced material is charged from the briquette-manufacturing
apparatus and oxygen is supplied; and a redudng-coal-gas supply tube for
supplying the reducing-coal-gas exhausted from the melter-gasifier to the multi-
stage fluidized-bed reactor unit
The apparatus for manufacturing molten iron according to the present
invention may further comprise a reformed-exhaust-gas supply tube which divides
the exhaust gas flow which is exhausted from the multi-stage fluidized-bed reactor
unit and supplies reformed exhaust gas from which CO2 is removed. An oxygen
burner may be mounted on the reducing-coal-gas supply tube for heating the
reducing coal gas mixed with the reformed exhaust gas, before supplying it to the
multi-stage fluidized-bed reactor unit
It is preferable that the reformed exhaust gas supply tube includes a gas
reformer for removing CO2 from the exhaust gas, which is exhausted through the
multi-stage fluidized-bed reactor unit and is divided.
It is preferable that the reformed exhaust gas supply tube includes a tar
remover for removing tar from the exhaust gas, which is exhausted through the
multi-stage fluidized-bed reactor unit and is divided.
It is preferable that the reformed exhaust gas supply tube includes a
compressor for compressing the exhaust gas, which is exhausted through the multi-
stage fluidized-bed reactor unit and is divided, and that the tar remover is mounted
on a front end of the compressor.
A cyclone, which charges dust exhausted from the melter-gasifier into the
melter-gasifier, may be provided to the melter-gasifier. The reformed-exhaust-gas
supply tube may be connected to a front end of the cyclone.
A transportation gas tube, by which the reformed exhaust gas from which
CO2 is removed is divided and through which the reformed exhaust gas is supplied
to the melter-gasifier as carrier gas for transporting dust separated in the cyclone,
may be connected to the rear end of the cyclone.
The multi-stage fluidized-bed reactor unit may comprise a first preheating
reactor which preheats the iron-containing mixture at a temperature of 400 to 500°C;
a second preheating reactor which is connected to the first preheating reactor and
which re-preheats the preheated iron-containing mixture at a temperature of 600 to
700°C; a pre-reducing reactor which is connected to the second preheating reactor
and which pre-reduces the re-preheated iron-containing mixture at a temperature of
700 to 800°C; and a final reducing reactor which is connected to the pre-reducing
reactor and which finally reduces the pre-reduced iron-containing mixture at a
temperature of 770 to 850°C.
Oxygen burners may be disposed between the second pre-heating furnace
and the pre-reducing reactor and between the pre-reducing furnace and the final
reducing reactor, and supply the reducing coal gas to each of the second pre-
heating reactor and the pre-reducing reactor after heating the reducing coal gas.
It is preferable that the reducing-coal-gas supply tube may be connected to
the final reducing reactor.
The apparatus for manufacturing molten iron according to the present
invention may further comprise a purging-coal-gas supply tube for purging the multi-
stage fluidized-bed reactor unit by dividing the reformed exhaust gas flow from
which CO2 is removed and by supplying the reformed exhaust gas to each of the
fluidized-bed reactors.
The apparatus for manufacturing molten iron according to the present
invention may further comprise an exhaust-gas-bypassing circulation tube which is
connected to the multi-stage fluidized-bed reactor unit and which supplies the total
amount of exhaust gas exhausted from the multi-stage fluidized-bed reactor unit to
the multi-stage fluidized-bed reactor unit.
The apparatus for manufacturing molten steel according to the present
invention may further comprise a coal gas re-supplying tube which divides reformed
exhaust gas flow from which CO2 is removed and supplies it into the melter-gasifier
together with oxygen during supplying oxygen thereto.
An integrated steel mill according to the present invention comprises the
above-mentioned apparatus for manufacturing molten iron, an apparatus for
manufacturing steel, which is connected to the apparatus for manufacturing molten
steel and which manufactures molten steel by removing impurities and carbon from
the molten iron; a thin slab casting machine which is connected to the apparatus for
manufacturing steel and which continuously casts the molten steel supplied from the
apparatus into thin slab; a hot-rolling machine which is connected to the thin slab
casting machine and which manufactures hot-rolled plate by hot-rolling the thin slab
discharged from the thin slab casting machine.
The apparatus for manufacturing steel may comprises: an molten-iron pre-
treatlng apparatus which is connected to the apparatus for manufacturing molten
iron and which removes phosphorus and sulfur contained in the molten iron
discharged form the apparatus; a decarbonization apparatus which is connected to
the molten Iron pre-treating apparatus and which removes carbon and impurities
contained in the molten iron discharged from the molten iron pre-treating apparatus;
and a ladle which is connected to the decarbonization apparatus and which
manufactures molten steel by refining again the molten iron discharged from the
decarbonization apparatus.
The integrated steel mill according to the present invention, may further
comprise a second multi-stage fluidized-bed reactor unit which divides reformed
discharged gas from which CO2 is removed and which converts fine iron-containing
ores to a reduced material; and a second briquette-manufacturing apparatus which
is connected to the first multi-stage fluidized-bed reactor unit and which
manufactures briquettes by briquetting the reduced material at a high temperature.
The second briquette-manufacturing apparatus may supply the reduced iron
briquettes to a decarbonization apparatus.
The second multi-stage fluidized-bed reactor unit may comprises: a
preheating reactor for preheating the fine iron-containing ores at a temperature of
600 to 700°C; a pre-reduclng reactor which is connected to the pre-heating reactor
and pre-reduces the preheated fine iron-containing ores at a temperature of 700 to
800°C; and a final reducing reactor which is connected to the pre-reducing reactor
and finally reduces the pre-reduced fine iron-containing ores at a temperature of 770
to 850°C.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other features and advantages of the present invention will
become more apparent by describing in detail exemplary embodiments thereof with
reference to the accompanying drawings in which :
Fig. 1 is schematic diagram illustrating an apparatus for manufacturing
molten iron according to an embodiment of the present invention;
Fig. 2 is a graph illustrating a relationship between an appropriate amount
of high-temperature-reducing gas and an amount of high-temperature-reducing gas
generated in a melter-gasifier;
Fig. 3 is a schematic diagram illustrating a circulation process of circulating
reducing coal gas in the apparatus for manufacturing molten iron according to the
embodiment of the present invention;
Fig. 4 is a schematic diagram Illustrating a circulation process of circulating
reducing coal gas after closing a melter-gasifier in the apparatus for manufacturing
molten iron according to the embodiment of the present invention;
Fig. 5 is a schematic diagram illustrating a purge process of purging the
apparatus for manufacturing molten iron according to the embodiment of the present
invention;
Fig. 6 is a graph illustrating relationship between a degree of oxidation
depending on temperatures and Fe mixture inside multi-stage fluidized-bed reactor
unit of the apparatus for manufacturing molten iron according to the embodiment of.
the present invention;
Fig. 7 is a view illustrating an embodiment of an Integrated steel mill
employing the apparatus for manufacturing molten iron according to the
embodiment of the present invention; and •
Fig. 8 is a view illustrating another embodiment of the integrated steel mill
employing the apparatus for manufacturing molten iron according to the
embodiment of the present Invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, exemplary embodiments of the present invention will be described
with reference to the attached drawings. However, the present invention can be
embodied in various modifications and thus is not limited to the embodiments
described below.
Fig. 1 is a diagram schematically illustrating an apparatus 100 for
manufacturing molten Iron according to an embodiment of the present invention,
which uses directly fine or lump coals and fine iron-containing ores.
The apparatus 100 for manufacturing molten iron according to the
embodiment of the present invention comprises a melter-gasifier 10, a multi-stage
fluidized-bed reactor unit 20, a briquette-manufacturing apparatus 30 for
manufacturing briquettes, a briquetter 40 for manufacturing briquettes, and a
reducing-coal-gas supply tube L50 as main components. The apparatus 100 may
comprise other subsidiary facility as needed.
As shown in Fig. 1, in the apparatus 100 for manufacturing molten iron
according to the embodiment of the present invention, room-temperature-fine ores
containing iron and supplementary raw materials having a grain size of 8 mm or less
are temporarily stored at a hopper 21, then they are mixed to produce Iron-
containing mixture. The resultant mixture is dried at a dryer 22, and then is
charged into a first preheating reactor 24 of the multi-stage fluidized-bed reactor unit
20. A uniform-pressure charging apparatus 23 is provided between the drier 22
and the first preheating reactor 24, such that the mixture at a normal pressure can
be charged into the multi-stage fluidized-bed reactor unit 20 which is maintained
within a range of 1.5 to 3 atmospheres.
The iron-containing mixture is in contact with a reducing gas flow
discharged from the melter-gasifier 10 and is reduced to about 90% which is a target
reduction ratio while sequentially passing through the first preheating reactor 24, a
second preheating reactor 25, a pre-reducing resctor 26, and a final reducing
reactor 27, which are connected in this order. A temperature of the iron-containing
mixture is raised at more than 800°C while it is reduced by the contact with the
reducing-coal-gas flow and the iron-containing mixture is converted to a high-
temperature-reduced material while more than 30% of the supplementary raw
materials in the iron-containing mixture is sintered. The multi-stage fluidized-bed
reactor unit 20 is embodied for four stages. However, the number of the fluidized-
bed reactors is for illustrative purpose only and is not meant to restrict the present
invention. Accordingly, the fluidized-bed reactor unit 20 needs to be embodied only
for multi-stages.
The reduced material which is reduced by the above-mentioned method
has a mean grain size of about 2.0 mm. The direct charging of the reduced
material into the melter-gasifier 10 brings about a significant scatter loss and
deterioration of a ventilation property of coal packed bed in the melter-gasifier 10.
Therefore, the reduced material discharged from the final reactor 27 is transferred to
the briquette-manufacturing apparatus 30 which is connected to the final reducing
reactor 27. Here, since the pressure inside the final reducing reactor 27 is
maintained at 3 atmospheres and the pressure inside the briquette-manufacturing
apparatus 30 is maintained at normal pressure, the reduced material is transferred
from the final reducing reactor 27 to the briquette -manufacturing apparatus 30 due
to the pressure difference.
In the briquette-manufacturing apparatus 30, the high-temperature reduced
material passed through the final reducing reactor 27 is temporarily stored at a
charging hopper 31 and is mechanically pressure-formed into briquettes having the
shape of strip while it is passed between a pair of rolls at a high temperature. Next,
the briquettes having the shape of strip are crushed by a crusher 35 to have a size
appropriate for charging it into the melter-gasifier 10 and the crushed briquettes are
stored at a storage bin 37. The briquettes are directly briquetted at a high
temperature to have predetermined strength and size. It is preferable that the grain
size of the briquette is 3 to 30 mm, and density is about 3.5 to 4.2 tons/m3. When
the grain size of the briquette is less than 3 mm, the ventilation property deteriorates
at the time of being charged into the melter-gasifier 10. When the grain size of the
briquettes is larger than 30 mm, it is difficult to manufacture the briquettes and hot-
strength deteriorates. The briquettes temporarily stored at the storage bin 37 is
continuously charged into the melter-gasifier 10 via the high-temperature uniform-
pressure charging apparatus 12 which allows the briquettes at a normal pressure to
be charged into the melter-gasifier 10 maintained within a range of 3.0 to 3.5 .
atmospheres.
On the other hand, a coal packed bed is formed inside the melter-gasifier
10, as a heat source to melt the briquettes. Raw coals to form the coal packed bed
inside the melter-gasifier 10 need to have a grain size of 10 to 50 mm. Lump coals
having such a grain size are directly into the melter-gasifier 10. On the other hand,
remaining fine coals go through a particle-size sorting process. The briquetter 40
crushes the fine coals having a grain size of 10 mm or less among the fine coals
stored in the storage hopper 41, into fine coals having a grain size of 4 mm or less.
The crushed fine coals are mixed with an appropriate amount of binder and
addictives by mixer 43. Resultant mixture is transported to a briquetter 45 and is
mechanically pressure-formed into briquettes. In this case, it is preferable that the
grain size of the briquette is about 30 to 50 mm and density thereof is 0.8 tons/m3.
When the grain size of the briquette is less than 30 mm, the ventilation property
inside the melter-gasifier 10 deteriorates. When the grain size of the briquette is
larger than 50 mm, it is difficult to manufacture the briquettes and warm-strength
deteriorates. The pressure-formed briquettes are stored in a storage bin 47.
The briquettes stored in the storage bin 47 are charged into the melter-
gasifier 10 together with lump coals to form coal packed bed. The briquettes
charged into the melter-gasifier 10 are gasified by pyrolysis reaction which occurs at
the upper side of the coal packed bed and by combustion reaction which occurs at
the lower side of the coal packed bed by use of oxygen. High-temperature-
reducing gas generated at the melter-gasifier 10 by the gasification reaction is
supplied to the multi-stage fluidized-bed reactor unit 20 via the redudng-coal-gas
supply tube L50 which is connected to a rear end of the final reducing reactor 27.
The high-temperature reducing gas is utilized as a reducing agent and fluidized gas.
The reducing coal gas reduces and sinters the iron-containing mixture while
sequentially flowing through the final reducing reactor 27, the pre-reducing reactor
26, the second preheating 25, and the first preheating reactor 24. The reducing
coal gas is exhausted from the first preheating reactor 24 and is dusted and cooled
while flowing through a dust collector 51 using water.
A dome-shaped empty space is formed above the coal packed bed of the
melter-gasifier 10, thereby reducing a gas flow rate. As a result, it is possible to
prevent fine coals contained in the briquette and fine coals generated due to the
abruptly-rising temperature of the coal which is charged into the melter-gasifier 10
from being discharged out of the melter-gasifier 10 in large quantities. Further, the
dome-shaped empty space absorbs variation in pressure in the melter-gasifier 10
that is caused by irregular changes in the amount of gas as a result of directly using
coal. The coal is gasified and volatile matters are removed from the coal while it
drops to the bottom of the coal packed bed, and is ultimately burned by oxygen
supplied through tuyeres at the bottom of the melter-gasifier. While generated
combustion gas rises through the coal packed bed, it is converted to high-
temperature-reducing gas and is exhausted outside the melter-gasifier 10. Part of
the combustion gas is dusted and cooled while passing through a dust collector 53
using water such that pressure applied to the melter-gasifier 10 is maintained within
a range of 3.0 to 3.5 atmospheres. Further, reduced iron is finally reduced and
melted by the reducing gas and combustion heat generated by the coal gasification
and combustion while dropping in the coal packed bed together with the coal, and
then the resultant molten iron is discharged outside.
A cyclone 14 is mounted on the melter-gasifier 10 for collecting dust
discharged outside. The cyclone 14 collects the exhaust gas generated at the
melter-gasifier 10 and again supplies the collected dust to the melter-gasifier 10.
Further, the cyclone 14 supplies, as reducing coal gas, the collected exhaust gas to
the fluidized-bed reducing reactor unit 20. Carrier gas is supplied to the rear end of
the cyclone 14 for supplying dust separated at the cyclone 14 into the melter-gasifier
10.
On the other hand, the apparatus 100 for manufacturing molten iron
according to the embodiment of the present invention comprises apparatus for
supplementing reducing coal gas, when an amount of the high-temperature-
reducing coal gas generated from the melter-gasifier 10 is insufficient due to a
variation in operating condition and a variation of coal quality, compared to an
appropriate amount of high-temperature-reducing gas which has to be supplied to
the multi-stage fluidized-bed reactor unit 20. A process of supplementing the
reducing coal gas will be described in detail with reference to Fig. 2.
Fig. 2 is a graph illustrating a relationship between the appropriate amount
of high-temperature-reducing gas and the amount of high-temperature-reducing gas
generated in a melter-gasifier, in which the insufficient amount of high-temperature
reducing gas on the basis of reduction ratio of 90% is shown.
Due to the variations in operating condition in the melter-gasifier 10 (shown
in Fig. 1) and in the coal property, the amount of the high-temperature-reducing coal
gas generated from the melter-gasifier 10 may be insufficient, compared to the
appropriate amount of high-temperature reducing gas which has to be supplied to
the multi-stage fluidized-bed reactor unit 20 (shown in Fig. 1). At this time, the
operating condition of the multi-stage fluidized-bed reactor unit 20 is adjusted to
prevent a deterioration in the reduction ratio of fine reduced iron passed through the
multi-stage fluidized-bed reactor unit 20 and a phenomenon in which heat inside the
melter-gasifier 10 becomes insufficient due to smelting of reduced Iron with low
reduction ratio.
In Fig. 2, a curved line D represents a relationship between the reduction
ratio and a gas basic unit. Curved lines A to C represent a relationship between
reduction ratio and an amount of gas generated In the melter-gasifier 10 which is
converted into the gas basic unit, depending on an amount of volatile matters
contained in the coal.
For example, when a target reduction ratio is 90%, an amount of the
reducing coal gas needed is 1400 Nm3 per 1 ton of the fine iron-containing ores in
the curved line D. On the contrary, when each amount of the volatile matters
contained in the coal is 23%, 26%, and 30%, each amount of reducing coal gas is
850 Nm3, 950 Nrn3, and 1050 Nm3 per 1 ton of the fine iron-containing ores, such
that 550 Nm3, 450 Nm3, and 350 Nm3 are needed in respective cases. When the
iron containing mixture Is reduced in multi-stage fluidized-bed reactor unit 20 in a
state in which the reducing coal gas is insufficient, the molten iron having a desired
property cannot be obtained. Therefore, the desired reduction ratio of the reduced
material can be obtained by supplementing the amount of reducing coal gas.
The apparatus 100 for manufacturing molten iron shown in Fig. 1 further
comprises a reformed-exhausted-gas supply tube L51 which divides the exhaust
gas flow which is exhausted from the multi-stage fluldized-bed reactor unit 20 and
supplies reformed exhaust gas from which CO2 is removed. The reformed-
exhaust-gas supply tube L51 is provided with a compressor 76 and a gas reformer
77 for removing CO2 contained in the exhaust gas exhausted from the first
preheating reactor 24. Further, a tar remover is provided at a front end of the
compressor 76 and removes a small amount tar contained in the gas, which is
supplied to the compressor 76, thereby preventing the tar from condensing inside
the compressor 76.
In the apparatus 100 for manufacturing molten iron, part of exhaust gas
flow exhausted from the first preheating reactor 24 and passed through the dust
collector 51 using water is divided and is passed through the tar remover 75. Then,
the exhaust gas is compressed by the compressor 76 and is reformed through the
gas reformer 77. The reformed exhaust gas is finally supplied to the multi-stage
fluidized-bed reactor unit 20 via a valve V772 to supplement an insufficient amount
of the reducing coal gas. In this case, the reformed exhaust gas is supplied to the
multi-stage fluidized-bed reactor unit 20 after being mixed with the reducing coal gas.
Since a temperature of the reducing coal gas decreases after being mixed with the
exhaust gas, the mixed gas is heated to a temperature needed for reduction by
using an oxygen burner 70 provided to the reduclng-coal-gas supply tube L50
before the mixed gas is supplied to the multi-stage fluidized-bed reactor unit 20.
Following various effects can be obtained through the above-described processes.
First, the reformed-exhaust-gas supply tube L51 is connected to the front
end of the cyclone 14 and room-temperature-reformed exhaust gas is supplied to
the cyclone 14, thereby preventing the cyclone 14 from being overheated.
Therefore, the cyclone 14 effectively collects the dust exhausted from the melter-
gasifier 10, thereby preventing the dust from being scattered.
Since the high-temperature-reducing coal gas exhausted from the melter-
gasifier 10 is mixed with the room-temperature-reformed exhaust gas, the
temperature of the reducing coal gas is lower than the temperature needed for its
supply to the multi-stage fluidized-bed reactor unit 20. As a result, it is difficult to
obtain the desired reduction ratio of the reduced material. Therefore, the reduction
ratio of the reduced material is raised by adjusting the temperature of the reducing
coal gas mixed with the reformed exhaust gas to a temperature needed for the
reduction by use of the oxygen burner. Specially, in the case of the apparatus 100
for manufacturing molten iron, since the temperature of the exhaust gas passed
through the multi-stage fluidized-bed reactor unit 20, that is, the temperature of the
exhaust gas finally passed through the first preheating reactor 24 is relatively low, an
amount of consumed water during the time of cooling the exhaust gas by using the
dust collector 51 using water is small. Therefore, the manufacturing cost is saved.
Further, in the case of the dust and the tar existing on the upper side of the
melter-gasifier 10, since the reducing coal gas is circulated as a reformed exhaust
gas after flowing through the multi-stage fluidized-bed reactor unit 20, a path for
circulating the dust and the tar with the reducing coal gas is sufficiently secured,
thereby a considerable amount of the dust and the tar is removed. Therefore, it is
possible to prevent the operation of the dust collector 51 using water from being
disturbed due to the condensation of the tar on the dust collector 51 using water.
Further, in case that the small-sized tar remover 75 is mounted on the front end of
the compressor 76, it is also possible to prevent the compressor 76 and the gas
reformer 77 from being damaged due to the condensation of the tar.
In the exhaust gas passed through the dust collector 51 using water, the
exhaust gas is comprised of CO of 35 volume%, H2 of 20 volume%, and CO2 of 40
volume%. Therefore, it is preferable to remove CO2 using the gas reformer 77 in
order to increase the reduction ratio. The amount of divided exhaust gas is
adjusted to 60 volume% or less of a total amount of the exhaust gas which is
exhausted from the fluidized-red reactor unit 20. Therefore, even though the
amount of reducing coal gas to be supplied to the multi-stage fluidized-bed reactor
20 is insufficient, it is possible to supplement the insufficient amount of the reducing
coal gas. When the amount of divided exhaust gas is larger than 60 volume%, the
amount of reformed exhaust gas to be supplied to the multi-stage fluidized-bed
reactor unit 20 after being mixed with the reducing coal gas increases, whereby a
gas flow rate in the multi-stage fluidized-bed reactor unit 20 becomes fast. As a
result, a large amount of the iron-containing mixture scatters to the outside the multi-
stage fluidized-bed reactor unit 20 and is lost.
Further, the amount of reducing gas to be supplied to the multi-stage
fluidized-bed reactor unit 20 is adjusted within a range of 1050 to 1400 Nm3 with
respect to 1 ton of the fine iron-containing ores to be charged into the multi-stage
fluidized-bed reactor unit 20, thereby effectively reducing the fine iron-containing
ores supplied to the multi-stage fluidized-bed reactor unit 20. Specifically, when the
amount of reducing gas supplied to the multi-stage fluidized-bed reactor unit 20 is
less than 1050 Nm3, It Is difficult to obtain a desired reduction ratio. When the
amount of reducing gas supplied to the multi-stage fluidized-bed reactor unit 20 is
larger than 1400 Nm3; the ore is reduced and sticks to each other due to an
oversupply of the reducing gas. Therefore, it is difficult to create a fluidized
reduction condition.
In case that CO2 is removed using the gas reformer 77, it is preferable that
an amount of the CO2 contained in the reformed exhaust gas passed through the
gas reformer 77 is 3.0 volume% or less. When the amount of CO2 is exceeds 3.0
volume%, the reducing power of the reformed exhaust gas decreases and the
reformed exhaust becomes not suitable to use.
As shown in Fig. 1, in the apparatus 100 for manufacturing molten iron
according to the embodiment of the present invention, part of the exhaust gas flow
passed through the dust remover 51 using water is divided and is passed through
the tar remover 75. The exhaust gas is compressed by the compressor 76 and is
reformed through the gas reformer 77. Then, the reformed exhaust gas can be
used as a carrier gas for charging the dust separated in the cyclone 14 into the
melter-gasifier 10 after a valve V771 mounted on a carrier gas tube L52 is.opened.
In case that the reformed exhaust gas is used as the carrier gas, an amount of
nitrogen which is used as the carrier gas can be reduced and a combustion rate can
be increased.
By opening a valve V773 mounted on a reducing gas re-supply tube L53,
the divided reformed exhaust gas flow from which CO2 is removed can be supplied
to the melter-gasifier 10 during the time of supplying oxygen thereto. Therefore, an
amount of the used briquettes can be reduced by supplying the reformed exhaust
gas to the melter-gasifier 10 and a gas flow distribution inside a char bed can be
improved.
Fig. 3 is a schematic diagram illustrating a circulation process of circulating
reducing coal gas in the apparatus 100 for manufacturing molten iron according to
the embodiment of the present invention. In Fig. 3, bold solid lines represent
circulation tubes through which the reducing coal gas is circulated. The other tubes
irrelative to the circulation tubes are represented as dotted lines. In case of a
closed valve, when the reducing coal gas is circulated, the reducing coal gas is
actually filled to a front end of the valve. Therefore, it needs to be indicated in the
figure, but it is omitted for the purpose of convenience in Fig. 3.
As shown in Fig. 3, the exhaust gas which is compressed and reformed can
be controlled by using valves mounted on tubes. Specifically, when the amount of
the reducing coal gas needed for reduction in the multi-stage fluidized-bed reactor
unit 20 is insufficient, in the apparatus 100 for manufacturing molten iron according
to the embodiment of the present invention, valves V51 to V53, V27, V762, and
V772 are opened, and the others closed, thereby supplementing the multi-stage
fluidized-bed reactor unit 20 with the reducing coal gas. The method of
supplementing the reducing gas shown in Fig. 3 is for illustrative purpose only and is
not meant to restrict the present invention.
Fig. 4 is a schematic diagram illustrating a circulation process of circulating
reducing coal gas after closing the supply of the reducing coal gas from the melter-
gasifier 10 to the multi-stage fluidized-bed reactor unit 20, In the apparatus 100 for
manufacturing molten iron according to the embodiment of the present invention.
Bold solid lines represent circulation tubes through which the reducing coal gas is
circulated. The other tubes irrelative to the circulation tubes are represented as
dotted lines. In case of a closed valve, when the reducing coal gas is circulated,
the reducing coal gas is actually filled to a front end of the valve. Therefore, it
needs to be indicated in the figure, but it is omitted for the purpose of convenience in
Fig. 4.
This process is related to the case in which the melter-gasifier 10 is tripped
and it is impossible to supply the reducing gas to the multi-stage fluidized reactor
unit 20. In this case, the whole amount of exhaust gas which is exhausted from the
multi-stage fluidized-bed reactor unit 20 is bypassed through a exhaust-gas-bypass
circulation tube L54 and is supplied to the multi-stage fluidized-bed reactor unit 20.
Further, in the melter-gasifier 10, the trip is occasionally generated due to
trial trouble. In this case, since gas is not generated in the melter-gasifier 10, it is
needed to circulate the exhaust gas to maintain bobble fluidized-bed in the multi-
stage fluidized-bed reactor unit 20 connected to the melter-gasifier 10. In this case,
the charging of the briquettes, the lump coals and the briquettes is stopped and the
exhaustion of the reducing gas from the melter-gasifier 10 is stopped to close the
melter-gasifier 10. Then, the valve V762 is closed. The whole exhaust gas
exhausted from the multi-stage fluidized-bed reactor unit 20 is passed through the
valve V51 and is compressed by the compressor 76. At the same time, the valve
V761 mounted on the exhaust-gas-bypass circulation tube L54 is opened and the
exhaust gas is supplied to the multi-stage fluidized-bed reactor unit 20. In this way,
the exhaust gas is continuously circulated. The valves V27, V53, V771, V772, and
V773 are all closed in this process to prevent the exhaust gas from leaking toward
the melter-gasifier 10. Therefore, it is possible to continuously circulate the
exhaust gas while preventing the exhaust gas from leaking inside the melter-gasifier
10. As a result, it is possible to prevent the collapse of the bubble fluidized-bed.
Fig. 5 is a schematic diagram illustrating a purge process of purging the
apparatus 100 for manufacturing molten iron according to the embodiment of the
present invention. Pipes, through which part of the compressed and reformed
exhaust gas is circulated to purge the multi-stage fluidized-bed reactor unit 20, are
represented as bold solid lines. In case of a closed valve, when the reducing coal
gas is circulated, the reducing coal gas is actually filled to a front end of the valve.
Therefore, it needs to be indicated in the figure, but it is omitted for the purpose of
convenience in Fig. 5.
When purge is needed during operation, the reformed exhaust gas for
purging is supplied to the multi-stage fluidized-bed reactor unit 20 via a purging-
coal-gas supply tube L55. Since a general operation is continuously performed
while such a purge is performed, part of the reformed exhaust gas is mixed with
exhaust gas from the melter-gasifier 10 via the reformed-exhaust-gas supply tube
L51 and is supplied to the multi-stage fluidized-bed reactor unit 20, and part of the
reformed exhaust gas is supplied to the tuyere of the metter-gasifier 10 or a dust
burner via carrier gas tube L52 and the reducing gas re-supply tube L53 in the same
way as during ordinary operation. Such a reformed exhaust gas flow is
represented by bold solid lines.
The multi-stage fluidized-bed reactor unit 20 comprises inner devices such
as a cyclone, a standpipe, a riser pipe, and a dumping line, which are built therein.
It is necessary to maintain a fluidized state in the inner devices such that the
reducing coal gas and the iron-containing mixture can be continuously fluidized.
Therefore, it is necessary to provide a purge line to prevent the inner device from
being blocked. The purge is generally performed by using nitrogen gas. However,
when the reducing coal gas is used for purge, additional nitrogen gas is not needed,
thereby considerably reducing the amount of nitrogen consumed.
In case that the purge is performed by using nitrogen gas, since the
exhaust gas flow which is exhausted from the multi-stage fluidized-bed reactor unit
20 is divided and reformed and then is again circulated into the multi-stage fluidized-
bed reactor unit 20, nitrogen is accumulated in the reformed exhaust gas and
nitrogen concentration in the whole reducing coal gas supplied to the multi-stage
fluidized-bed reactor unit is ultimately increased. As a result, when the
concentration of nitrogen, which Is inactive gas, exceeds 10.0 volume% of the whole
reducing coal gas, the reduction ratio of the ore at the multi-stage fluidized-bed
reactor unit 20 decreases. Therefore, as described above, nitrogen concentration
in the reducing coal gas is reduced to 10.0 volume% or less by using the reformed
exhaust gas as the purge gas. Thus, it is possible to prevent nitrogen from being
accumulated in the reducing coal gas to be supplied to the multi-stage fluidized-bed
reactor unit 20.
The exhaust gas flow which is exhausted through the multi-stage fluidized-
bed reactor unit 20 is divided and CO2 is removed from the exhaust gas. The
reformed exhaust gas is supplied to each of the fluidized-bed reactors 20.
Although it is not shown in Fig. 5, the coal gas supply tube L55, which is connected
to each of the fluidized-bed reactors 20, is again divided to supply the reformed
exhaust gas to the inner devices of the respective fluidized-bed reactors 20 and can
purge the inner devices, as needed. Specifically, the amount of the reformed
exhaust gas, which is supplied as purge gas, can be controlled by using a valve V24
mounted on the purging-coal-gas supply tube L55.
Hereinafter, an operating condition of the multi-stage fluidized-bed reactor
unit 20 in a method of manufacturing molten iron according to the present invention
will be described in detail. Specifically, in the present invention, an optimal control
condition is determined taking into account the fact that it is significantly important to
reduce the iron-containing mixture using the reducing coal gas.
Fig. 6 is a graph illustrating relationship between a degree of oxidation and
Fe mixture depending on temperatures of the multi-stage fluidized-bed reactor unit
20 in the apparatus for manufacturing molten iron according to the embodiment of
the present invention, in which stable regions of Fe mixture phase in each of the
fluidized-bed reactors are illustrated.
Here, a degree of oxidation is calculated by using each amount of gas such
as CO, CO2, H2) and H2O contained in the reducing gas. The degree of oxidation
means a measure of reducing power. The degree of oxidation is defined as (CO2
volume% + H2O volume%)/(CO volume% + H2 volume% + CO2 volume% + H2O
volume%) x 100. In Fig. 6,100 - the degree of oxidation is used as value for a Y-
axis for the purpose of convenience, which means a degree of reduction as a
concept contrary to the degree of oxidation. Therefore, as it goes toward the upper
side of the Y-axis, a reduction reaction is easily generated. On the contrary, as it
goes toward the lower side of the Y-axis, an oxidation reaction is easily generated.
In the method of manufacturing molten iron according to an embodiment of
the present invention, the multi-stage fluidized-bed reactor unit 20 (shown in Fig. 1)
uses directly the coal gas as reducing gas. Therefore, it is possible to operate
under relatively low gas basic unit of 1400 Nnf/ton and relatively short resident time
of maximum sixty minutes with respect to each of the fiuidized reactors, compared
to other fluidized-bed reducing process such as FINMET, FIOR, IRON CARBIDE,
etc., which uses directly natural gas. Therefore, in the fiuidized reduction process,
as shown in Fig. 6, in case of a first preheating reactor in which a first step for
preheating the iron-containing mixture is performed, it is preferable that the fiuidized
reduction occurs at a Fe3O4 phase stable region. In case of a second preheating
reactor in which a second step for re-preheating the iron-containing mixture is
performed, it is preferable that the fiuidized reduction occurs at a FeO phase stable
region. In case of a pre-reducing reactor in which a third step for pre-reducing the
preheated iron-containing mixture is performed and a final reactor in which a fourth
step for finally reducing the pre-reduced iron-containing mixture are performed, It is
preferable that the fluidized reduction occurs at a Fe phase stable region. By
maintaining the above-described regions, it is possible to minimize the amount of
the iron-containing mixture stabilized into the Fe3O4 phase in which reaction speed
is very slow, while passing through the first preheating reactor and the second
preheating reactor. Further, it is possible to make the iron-containing mixture be
sufficiently reduced while passing through the pre-reducing reactor and the final
reactor in which the Fe phase stabilized region is formed.
In the multi-stage fluidized-bed reactor unit 20 in which the operation is
performed at the relatively low gas basic unit, it is important to adjust the
temperature of the respective fluidized reactors and the composition of the reducing
coal gas for securing the Fe phase stabilized region in each fluidized-bed reactor.
To create the fluidized reduction condition in each of the fluidized-bed
reactors, it is preferable that the temperature of the bubble fluidized-bed of the first
preheating reactor is maintained in a range of 400 to 500°C, the temperature of the
bubble fluidized-bed of the second preheating reactor is maintained in a range of
600 to 700°C, the temperature of the bubble fluidized-bed of the pre-reducing
reactor is maintained in a range of 700 to 800°C, and the temperature of the bubble
fluidized-bed of the final reducing reactor Is maintained in a range of 770 to 850*C.
Further, it is preferable that the composition of the reducing coal gas supplied to
each of the fluidized-bed reactor is maintained to secure a certain degree of
oxidation in each of the fluidized-bed reactors, specifically, 45% or more in the first
preheating reactor, 35% to 50% in the second preheating reactor, and 25% or less in
the pre-reducing reactor and the final reducing reactor.
Concerning the suitable temperature and the composition of the reducing
coal gas in each of the reactors for maintaining above-mentioned condition, the
temperature of the reducing coal gas which is exhausted from the melter-gasifier
and which is supplied to the bubble fluidized-bed of the final reactor is too high, that
is, the temperature is about 1000°C. Therefore, when the reducing coal gas is
supplied to the final reactor as it is, the iron-containing mixture in the final reactor is
overheated and sticking is generated between ores. Therefore, it is necessary to
cool down the reducing coal gas supplied to the final reactor. The cooling of the
final reactor is made possible by mixing the room-temperature reformed exhaust gas
and the reducing coal gas exhausted from the melter-gasifier. Further, the supplied
amount of room-temperature reformed exhaust gas is adjusted depending on the
amount of the reducing gas required by the final reactor. As a result, the reducing
coal gas supplied to the final reactor during mixing process may be overcooled
below a suitable temperature. Therefore, the temperature of the reducing coal gas
is maintained to be a suitable temperature by supplying oxygen to the reducing coal
gas and by partially combusting the reducing coal gas, after mixing the room-
temperature reformed exhaust gas with the reducing coal gas.
Further, a burner 72 is mounted between the second preheating reactor 25
and the pre-reducing reactor 26 and a burner 71 is mounted between the pre-
reducing reactor 26 and the final reactor 27 for supplying oxygen to the reducing
coal gas which is exhausted from reactors 20 and for partially combusting the
reducing coal gas. Through this method, the degree of oxidation of the reducing
coal gas in the bubble fluidized-bed of the pre-reducing reactor 26 is maintained at
35% or less. Further, the degree of oxidation of the reducing coal gas in the bubble
fluidized-bed of the second preheating reactor 26 is maintained within a range of
40% to 60%. Further, the reducing coal gas which is exhausted from the second
preheating reactor 25 is supplied to the bubble fluidized-bed of the first preheating
reactor 24 as it is. As a result, the degree of oxidation of the multi-stage fluidized-
bed reactor unit 20 is adjusted.
Therefore, according to the present invention, when the amount of the
reducing coal gas is insufficient in the above-mentioned actual process, it is possible
to supplement the insufficient amount and to meet the ideal operation condition of
the multi-stage fluidized-bed reactor unit 20.
In table 1, a temperature of fluidized-bed and a degree of oxidation of the
reducing gas for each of reactors in a four-stage fluidized-bed reactor unit 20, and
Fe-0 phase contained in ore discharged from each of fluidized-bed reactors in each
stage are shown.
[Table 1]
In table 1, a gas basic unit is 1200 Nnf/t-ore. As shown in table 1, by
controlling the temperature of the fluldized-bed and the degree of oxidation for each
of thefluidized-bed reactors in the multi-stage fluidized-bed reactor unit 20 within the
above-described range, the amount of Fe3O4 formed in the first preheating reactor Is
minimized and the Fe3O4 is not further formed in the second preheating reactor. As
a result, a reduction ratio of 80% or more with respect to fine iron-containing oVes
can be obtained in the final reactor by reducing the FeO into Fe.
In the above-mentioned apparatus 100 for manufacturing molten iron, fine
or lump coals and fine Iron-containing ores can be directly used and the apparatus
100 is compact on the whole, such that it is suitable to use the apparatus 100 in an
integrated steel mill by connecting the apparatus 100 to the integrated steel mill.
Therefore, it is possible to directly manufacture a hot-rolled steel plate from the fine
or lump coals and fine iron-containing ores by employing the apparatus 100 for
manufacturing molten iron according to the embodiment of the present invention in a
mini-mill process, which is an integrated steel manufacturing process.
Hereinafter, an integrated steel mill employing the apparatus 100 for
manufacturing molten iron according to the embodiment of the. present invention will
be described in detail. Such an integrated steel mill is for illustrative purpose only
and is not meant to restrict the present invention.
Fig. 7 is a view illustrating an embodiment of an integrated steel mill 1000
employing the apparatus 100 for manufacturing molten iron according to the
embodiment of the present invention. In Fig. 7, the integrated steel mill 1000 for
directly manufacturing a hot-rolled steel plate from fine or lump core and fine iron-
containing ores is schematically illustrated. The apparatus 100 for manufacturing
molten iron shown in Fig. 7 has the same structure as the above-mentioned
apparatus 100 for manufacturing molten iron according to the embodiment of the
present invention, therefore the description thereof is omitted for the purpose of
convenience. Hereinafter, the other apparatus except the apparatus 100 for
manufacturing molten iron will be described.
The integrated still mill shown in Fig. 7 comprises the apparatus 100 for
manufacturing molten iron, an apparatus for manufacturing steel 200 which is
connected to the apparatus 100 for manufacturing molten steel and which
manufactures molten steel by removing impurities and carbon from the molten iron,
a thin slab casting machine 300 which is connected to the apparatus 200 for
manufacturing steel and which continuously casts the molten steel supplied from the
apparatus into thin slab, a hot-rolling machine 400 which is connected to the thin
slab casting machine 300 and which manufactures hot-rolled plate by hot-rolling the
thin slab discharged from the thin slab casting machine 300. In addition, the
integrated steel mill 1000 may comprise further apparatus as needed.
Fig. 7 illustrates in detail an example of process of manufacturing steel by
employing the above-mentioned apparatuses. The apparatus 200 for
manufacturing steel comprises a molten-iron pre-treating apparatus 61 which
removes phosphorus and sulfur contained in the molten iron, a decarbonization
apparatus 64 which is connected to the molten iron pre-treating apparatus 61 and
which removes carbon and impurities contained in the molten iron discharged from
the molten iron pretreatment apparatus 61, and a ladle 67 which is connected to the
decarbonization apparatus 64 and which manufactures molten steel by refining
again the molten iron discharged from the decarbonization apparatus 64.
The molten iron discharged from the melter-gasifier 10 is periodically
discharged to the molten iron pretreatment apparatus 61 having a refractory
container and is transported to a downstream process. A molten-iron pre-treatment
is performed during the transportation by blowing desulfurizing agent, which is flux,
In the molten iron contained in the molten iron pretreatment apparatus 61 and by
removing sulfur and phosphorus components contained in the molten iron. As a
result, sulfur component in the molten iron is adjusted to 0.006% or less. It is
preferable that CaO or CaCO3 is used as the desulfurizing agent in the molten iron
pretreatment process.
Further, the molten iron in the molten Iron pretreatment apparatus, which
went through the molten iron pretreatment, is discharged into a decarbonization
apparatus 64 in a converter type. In the process of discharging, it is preferable that
molten slag, which is generated in the molten iron pretreatment process and is
floated on the molten iron, does not infiltrate into the decarbonization apparatus 64.
An oxidation refining is performed by blowing oxygen at a high speed into the molten
iron after the molten iron is supplied to the decarbonization apparatus 64. During
the oxidation refining, impurities which are dissolved in the molten iron such as
carbon, silicon, phosphorus, and manganese are removed by oxidation and the
molten iron is converted to molten steel. The oxidized impurities are dissolved into
the molten slag on the molten steel by CaO, CaF2, dolomite, eta which are supplied
to the converter and are separated from the molten steel. After the oxidation
refining is finished, the molten steel is discharged from the decarbonization
apparatus 64 into the ladle 67, which is a refractory container and then is
transported to a downstream process. Through such a process of manufacturing
steel, an amount of carbon contained in the molten steel is adjusted to 2.0 wt% or
less.
The molten steel goes through a second refining process in the ladle 67.
The molten steel is heated by an electrical arc, which is generated on the molten
steel by a high voltage transferred through an electrode rod, and is agitated by
inactive gas blown from the bottom of the ladle 67, such that a uniform distribution of
temperature and component and a floatation separation of nonmetallic interposed
materials inside the molten steel is achieved. Further, a sulfur component, which is
existed in the molten steel in a small amount, can be vigorously removed by blowing
Ca-SI powers into the molten steel, as needed. Further, after the above-mentioned
processes are finished, the molten iron goes through a gas removing process in
which a vacuum bath is connected to the upper side of the refractory container to
generate a vacuum state and gas components such as carbon, N2, and H2 are
removed, thereby increasing a degree of purity of the molten steel. It is preferable
to prevent the temperature of the molten steel from being lowered by using
combustion heat generated by blowing oxygen during the gas removing process and
by combusting the exhausted gas component
The ladle 67 is transported to the thin slab casting machine 300 after the
above-mentioned second refining process. The molten steel is discharged from the
ladle 67 to tundish 71, which is located above the thin slab casting machine 300,
and is supplied to the thin slab casting machine 73 from the tundish 71 to cast a thin
slab having a thickness of 40 mm to 100 mm. The cast thin slab is compressed
through a rough rolling mill 75, which is directly connected to the casting machine 73,
into a bar shape having a thickness of 20 to 30 mm. Then, the compressed thin
slab is heated by the heater 77 and is wound on a winder 79. When the thickness
of the thin slab is smaller than 40 mm, it is easily broken. When the thickness of
the thin slab is larger than 100 mm, it may overload the tough rolling mill 75.
The wound bar is again unwound and is passed through a rust remover 83
to remove rust generated on a surface of the bar. Then, the bar is transported to a
final rolling mill and is rolled into a rolled steel plate having a thickness of 0.8 to 2.0
mm. The rolled steel plate is cooled by cooler 87 and Is wound 89 as a finally
rolled steel plate. Hot-rolled steel plate having a thickness of 0.8 to 2.0 mm is
suitable for a consumer to use.
In the integrated steel mill 1000 employing the apparatus 100 for
manufacturing molten iron according to the embodiment of the present invention,
there is an advantage that a hot-rolled steel plate can be manufactured directly
using fine or lump coals and fine iron-containing ores through above-described
processes. Therefore, raw material is not restricted at the time of manufacturing
molten iron and it is possible to manufacture a hot-rolled steel plate by using
compact facilities.
Fig. 8 is a view illustrating another embodiment of the integrated steel mill
2000 employing the apparatus 100 for manufacturing molten iron according to the
embodiment of the present invention. Fig. 8 illustrates a process of supplying
reduced iron to decarbonizatlon apparatus which is one element of an apparatus for
manufacturing steel by a second multi-stage fluidized-bed reactor unit 90 and a
second briquette-manufacturing apparatus 35 equipped to the integrated steel mill
2000. The integrated steel mill 2000 shown in Fig. 8 has the same structure as the
integrated steel mill 1000 except for some part Therefore, description of the same
part is omitted for the purpose of convenience and thus description of the other
portion will be described in detail.
Further, in the integrated steel mill 2000 to be described, the above-
described multi-stage fluidized-bed reactor unit 20 connected to the melter-gasifier
10 is referred to as a first fluidized-bed reactor unit and another multi-stage fluidized-
bed reactor unit is referred to as a second multi-stage fluidized-bed reactor unit
Further, the briquette-manufacturing apparatus 30, which is connected to the rear
end of the first multi-stage fluidized-bed reactor unit 20, is referred to as a first
briquette-manufacturing apparatus and another briquette-manufacturing apparatus
35 which is connected to a rear end of second fluidized-bed reactor unit 90 is
referred to as a second briquette-manufacturing apparatus.
As shown in Fig. 8, the integrated steel mill 2000 comprises second multi-
stage fluidized-bed reactor unit 90 and the second briquette-manufacturing
apparatus 35. The second multi-stage fluidized-bed reactor unit 90 is an
equipment for reducing fine iron-containing ores, which are supplied thereto from an
iron-containing ore hopper 91. The multi-stage fluidized-bed reactor unit 90 is
made of a three-stage fluidized-bed reactor unit comprising a first preheating reactor
93, a pre-reducing reactor 95 and a final reducing reactor 97. In each of the
reactors 93, 95, and 97, a bubble fluidized-bed is formed.
In the second multi-stage fluidized-bed reactor unit 90, the first preheating
reactor 93 preheats the fine iron-containing ores at a temperature of 600 to 700°C,
the pre-reducing reactor 95 connected to the preheating reactor 93 pre-reduces the
preheated iron-containing ores at a temperature of 700 to 800°C, and the final
reactor 97 connected to the pre-reducing reactor 95 finally reduces the pre-reduced
iron-containing ores at a temperature of 770 to 850°C.
The second multi-stage fluidized-bed reactor unit 90 is supplied with part of
exhaust gas exhausted from the first fluidized reactor unit 20 via an additional
reducing gas circulation pipe from the final reactor 97 and converts dried and mixed
iron-containing ores having a grain size of 8 mm or less to reduced iron which is
reduced over 92% while sequentially circulating the exhaust gas through each of the
reactors 93, 95, and 97. In Fig. 8, the second multi-stage fluidized-bed reactor unit
90 Is represented as a three-stage fluidized-bed reactor unit, but is for illustrative
purpose only and is not meant to restrict the present invention. The fluidized-bed
reactor unit 90 can be implemented to have various number of stage
Further, the second briquette-manufacturing apparatus 35 temporary stores
the high-temperature reduced iron at a charging hopper 36 and briquettes the
reduced iron by pressure-forming while passing the reduced iron through a pair of
roller 37. Then, the briquette Is crushed by a crusher 38 and stored at an briquette
supplying hopper 39.
It is preferable that the amount of the reducing coal gas supplied to the
second multi-stage fluidized-bed reactor unit 90 is 40 volume% or more of the total
amount of exhaust gas exhausted from the first multi-stage fluidized-bed reactor unit
20. On the other hand, in the process of supplying part of exhaust gas-exhausted
from the first multi-stage fluidized-bed reactor 20 to the second multi-stage fluidized-
bed reactor unit 90, tar is removed from the exhaust gas by a tar remover 75. It is
preferable that an amount of CO2 contained in the reformed exhaust gas is 3.0
volume% or less. The reducing coal gas passed through the second multi-stage
fluidized-bed reactor unit 90 is dusted and cooled by a dust collector 55 using water,
and then discharged outside.
Although not shown in Fig. 8, it is preferable that the reformed exhaust gas
is partially combusted by supplying oxygen thereto to raise a temperature of the
exhaust gas by use of combustion heat and the raised temperature is 800 to 850°C.
Since the reduced iron is manufactured by using the iron-containing ores
and the purified reducing gas, 90% or more of the reduced iron is comprised of pure
iron, and sulfur is contained in a very low concentration, whereby increasing a
degree of purity of the molten steel which is manufactured at the decarbonization
apparatus 64 when the reduced iron is charged into the decarbonization apparatus
64.
Hereinafter, the present invention will be described in detail with reference
an experimental example. However, this experimental example is for illustrative
purpose only and is not meant to restrict the present invention.
[Experimental Example]
Molten and slag is manufactured by the above-mentioned apparatus for
manufacturing molten iron according to the embodiment of the present invention.
In the experimental example according to the embodiment of the present
invention, the melter-gasifier 10. was maintained at 3.2 atmospheres and an amount
of oxygen supplied to combust coal inside the melter-gasifier 10 was adjusted to 550
Nm3 per 1 ton of molten iron. Further, amounts of fine ore and supplementary raw
materials were adjusted to 1.5 tons and 0.35 tons, respectively. An amount of coal
supplied to the melter-gasifier 20 was adjusted to 0.9 to 1.0 tons based on produced
molten iron of 1 ton. A production capacity of the apparatus for manufacturing
molten iron was determined to be 85 tons/hour under the above-described
operational condition.
An experimental operation was performed according to the embodiment of
the present invention and compositions of resultant molten iron and slag discharged
from the melter-gasifier were as follows. Table 2 shows a composition of molten
iron according to the embodiment of the present invention and Table 3 shows a
composition of slag according to the embodiment of the present invention.
(Table 2]
As shown in Table 3, the temperature of the molten iron manufactured by
the experimental example according to the present invention was about 1520°C and
the basicity was 1.15.
As can be understood from the Table 2, the temperature of the molten iron
manufactured according to the present invention was property 1500°C and the
amounts of Si, P, and S were so small that it could satisfy the molten iron quality
standard for general steel manufacture. Further, as can be understood from the
Table 3, the temperature of the slag was properly 1520°C and the basicity of the
slag, which is a measure of slag quality, was property 1.15. Therefore, in the
method of manufacturing molten iron according to the embodiment of the present
invention, even though the fine or lump coals and the fine iron-containing ores were
used differently from the conventional invention, the quality of the molten was similar
to that of the molten iron in the conventional method.
According to the present invention described above, since molten iron
having high quality satisfying the molten iron quality standard for manufacturing
steel can be continuously manufactured by directly using fine or lump coals or fine
iron-containing ores, it is possible to replace a blast furnace method which has been
in use in an integrated steel mill. Therefore, it is possible to use low-price raw
materials and to omit sintering and coke processes, thereby increasing economical
efficiency of the integrated steel mill and preventing the generation of pollution
materials during the sintering and coke processes.
Further, in the apparatus for manufacturing molten iron according to the
present invention, exhaust gas flow, which is exhausted from a multi-stage fluidized-
bed reactor unit, is divided and is reformed. The reformed exhaust gas is supplied
to the multi-stage fluidized-bed reactor unit. Therefore, it is possible to supplement
an insufficient amount of reducing coal gas, thereby securing operational flexibility.
Furthermore, room-temperature-reformed exhaust gas which is cooled can
be supplied to a front end of a cyclone, thereby preventing the cyclone from being
overheated.
According to the present invention, the exhaust gas, which is exhausted
from the multi-stage fluidized-bed reactor unit, is used as carrier gas, thereby
reducing an amount of nitrogen used as the carrier gas.
Further, the reformed exhaust gas which is reformed according to the
present invention can be again supplied to a melter-gasifier together with oxygen,
thereby reducing a coal consumption ratio and improving gas stream distribution in a
char-bed.
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 details may be made therein without
departing from the sprit and scope of the invention as defined by the appended
claims.
WE CLAIM :
1. A method of manufacturing molten iron, comprising the steps of:
manufacturing iron-containing mixture by mixing fine iron-containing ores
and supplementary raw materials and by drying the resultant mixture;
converting the iron-containing mixture to a reduced material by reducing
and sintering while passing the iron-containing mixture through a multi-stage
fluidized-bed reactor unit, of which fluidized-bed reactors are sequentially
connected to each other;
manufacturing briquettes by briquetting the reduced material at high
temperature;
forming a coal packed bed by charging lump coals and briquettes which
are made by briquetting fine coals, into a melter-gasifier as heat sources for
melting the briquettes;
manufacturing molten iron by charging the briquettes into the melter-
gasifier connected to the multi-stage fluidized-bed reactor unit and by supplying
oxygen into the melter-gasifier;
supplying reducing coal-gas exhausted from the melter-gasifier into the
multi-stage fluidized-bed reactor unit;
dividing the exhaust gas flow which is exhausted through the multi-stage
fluidized-bed reactor unit and removing CO2 from the exhaust gas;
mixing the reformed exhaust gas from which CO2 is removed with the
reducing coal gas which is exhausted from the melter-gasifier; and
heating the reducing coal gas mixed with the reformed exhaust gas before
supplying it to the multi-stage fluidized-bed reactor unit to adjust a temperature of
the reducing coal gas to a temperature required to reduce the iron-containing
mixture at the multi-stage fluidized-bed reactor unit.
2. The method as claimed in claim 1, wherein the reformed exhaust gas is
heated by using an oxygen burner, at the heating step before supplying the
reducing coal gas mixed with the reformed exhaust gas to the multi-stage
fluidized-bed reactor unit.

3. The method as claimed in claim 1, wherein, in the step of dividing the
exhaust gas flow which is exhausted through the multi-stage fluidized-bed
reactor unit and removing CO2 from the exhaust gas, an amount of divided
exhaust gas is preferably 60 volume% of a total amount of the exhaust gas
which is exhausted from the fluidized-bed reactors.
4. The method as claimed in claim 1, wherein the amount of the reformed
exhaust gas is maintained at a range of 1050 Nm3 to 1400 Nm3 per 1 ton of the
fine iron-containing ores.
5. The method as claimed in claim 1, wherein, in the step of mixing the
reformed exhaust gas from which CO2 is removed with the reducing coal gas
which is exhausted from the melter-gasifier, an amount of CO2 contained in the
reformed exhaust gas is preferably 3.0 volume% or less.
6. The method as claimed in claim 1, wherein the divided exhaust gas is
compressed at the step of dividing the exhaust gas flow exhausted from the
multi-stage fluidized-bed reactor unit and removing CO2 from the exhaust gas.
7. The method as claimed in claim 1, comprising a step of dividing the
exhaust gas flow which is exhausted through the multi-stage fluidized-bed
reactor unit and removing tar from the exhaust gas, before the step of dividing
the exhaust gas flow which is exhausted from the multi-stage fluidized-bed
reactor unit and removing CO2 from the exhaust gas.
8. The method as claimed in claim 1, wherein, in the step of mixing the
reformed exhaust gas from which CO2 is removed with the reducing coal gas
which is exhausted from the melter-gasifier, the reformed exhaust gas is mixed
at a front end of a cyclone which charges dust exhausted from the melter-gasifier
into the melter-gasifier.

9. The method as claimed in claim 8, wherein the reformed exhaust gas flow
from which CO2 is removed is divided and is used as carrier gas for charging dust
separated at the cyclone into the melter-gasifier.
10. The method as claimed in claim 1, comprising a step of bypassing a total
amount of exhaust gas which is exhausted from the multi-stage fluidized-bed
reactor unit and supplying it to the multi-stage fluidized-bed reactor unit during
the time of closing the melter-gasifier or before operating the melter-gasifier.
11. The method as claimed in claim 1, comprising the steps:
dividing the exhaust gas flow which is exhausted through the multi-stage
fluidized-bed reactor unit and removing CO2 from the exhaust gas flow; and
purging the multi-stage fluidized-bed reactor unit by dividing the reformed
exhaust gas flow from which CO2 is removed and by supplying the reformed
exhaust gas to each of the fluidized-bed reactors.
12. The method as claimed in claim 11, an amount of nitrogen contained in
the reducing coal gas is 10.0 volume% or less.
13. The method as claimed in claim 1, comprising the steps of:
dividing the exhaust gas flow which is exhausted through the multi-stage
fluidized-bed reactor unit and removing CO2 contained in the exhaust gas flow;
and
dividing the reformed exhaust gas flow from which CO2 is removed and
supplying it into the melter-gasifier together with oxygen during the time of
supplying oxygen thereto.
14. The method as claimed in claim 1, the step of converting the iron-
containing mixture to a reduced material comprises:
a first step of preheating the iron-containing mixture at a temperature of
400 to 500°C;

a second step of re-preheating the preheated iron-containing mixture at a
temperature of 600 to 700°C;
a third step of pre-reducing the re-preheated iron-containing mixture at a
temperature of 700 to 800°C; and
a fourth step of finally reducing the pre-reduced iron-containing mixture at
a temperature of 770 to 850°C.
15. The method as claimed in claim 14, wherein a degree of oxidation at the
first and second steps is 25% or less;
a degree of oxidation at third step is 35 to 50%;
a degree of oxidation at fourth step is 45% or more,
here, the degree of oxidation is obtained by a following equation: (CO2
volume% + H20 volume%)/(CO volume% + H2 volume% + CO2 volume% + H20
volume%) x 100; CO, CO2, H20 and H2 are gases, each of which is contained in
the reducing gas.
16. The method as claimed in claim 14, wherein the second and third steps
comprise a step of supplying oxygen.
17. The method as claimed in claim 1, wherein, in the step of manufacturing
the briquettes at a high temperature, the grain size of the briquettes are within a
range of 3 mm to 30 mm.
18. The method as claimed in claim 1, wherein, in the step of forming the coal
packed bed, the grain size of the briquette is within a range of 30 mm to 50 mm.
19. An integrated steel manufacturing method, comprising the steps of:
manufacturing molten iron by using the molten iron manufacturing method
as claimed in claim 1;
manufacturing molten steel by removing impurities and carbon contained
in the molten iron;

continuously casting the molten iron into thin slab;
hot-rolling the thin slab to make hot-rolled steel plate.
20. The integrated steel manufacturing method as claimed in claim 19,
wherein, in the step of continuously casting the molten iron into a thin slab, the
molten steel is continuously cast into thin slab having a thickness of 40 mm to
100 mm.
21. The integrated steel manufacturing method as claimed in claim 19,
wherein, in the step of hot-rolling the thin slab to make hot-rolled steel plate, the
hot-rolled steel plate is made to have a thickness of 0.8 mm to 2.0 mm.
22. The integrated steel manufacturing method as claimed in claim 20,
wherein the step of manufacturing the molten steel comprises the steps of:
pre-treating the molten iron to remove phosphorus and sulfur contained in
the molten iron;
removing carbon and impurities contained in the molten iron by supplying
oxygen into the molten iron; and
manufacturing the molten steel by removing impurities and dissolved gas
byway of second refining of the molten iron.
23. The integrated steel manufacturing method as claimed in claim 22,
comprising the steps of:
converting fine iron-containing ores to reduced iron by reducing the fine
iron-containing ores while passing it through a multi-stage fluidized-bed reactor
unit, of which reactors are sequentially connected to each other; and
manufacturing reduced-iron briquettes by briquetting the reduced iron at a
high temperature,
wherein, in the step of removing carbon and impurities contained in the
molten iron, the reduced-iron briquettes and the molten iron are mixed, and
carbon and impurities are removed therefrom.

24. The integrated steel manufacturing method as claimed in claim 23, the
step of converting the fine iron-containing ores to the reduced iron comprises the
steps of:
preheating the fine iron-containing ores at a temperature of 600 to 700°C;
pre-reducing the preheated fine iron-containing ores at a temperature of
700 to 800°C; and
final-reducing the pre-reduced fine iron-containing ores at a temperature
of 770 to 850°C to convert it to reduced iron.
25. An apparatus for manufacturing molten iron, comprising:
a multi-stage fluidized-bed reactor unit for converting fine iron-containing
ores which are mixed and dried and supplementary raw materials to reduced
material;
a briquette-manufacturing apparatus which is connected to the multi-stage
fluidized-bed reactor unit and which manufactures briquettes by briquetting the
reduced material at a high temperature;
a briquetter for manufacturing briquette, which is used as a heat source,
by briquetting fine coals;
a melter-gasifier for manufacturing molten steel, into which lump coals
and the briquettes manufactured from the briquetter are charged and a coal
packed bed being formed, and into which the reduced material is charged from
the briquette manufacturing apparatus and oxygen is supplied;
a reducing-coal-gas supply tube for supplying the reducing-coal-gas
exhausted from the melter-gasifier to the multi-stage fluidized-bed reactor unit;
said apparatus for manufacturing molten iron further comprising a
reformed-exhaust-gas supply tube which divides the exhaust gas flow which is
exhausted from the multi-stage fluidized-bed reactor unit and supplies reformed
exhaust gas from which CO2 is removed;
wherein an oxygen burner is mounted on the reducing-coal-gas supply
tube for heating the reducing coal gas mixed with the reformed exhaust gas,
before supplying it to the multi-stage fluidized-bed reactor unit.

26. The apparatus for manufacturing molten iron as claimed in claim 25,
wherein the reformed exhaust gas supply tube includes a gas reformer for
removing CO2 contained in the exhaust gas, which is exhausted through the
multi-stage fluidized-bed reactor unit and is divided.
27. The apparatus for manufacturing molten iron as claimed in claim 25,
wherein the reformed exhaust gas supply tube includes a tar remover for
removing tar from the exhaust gas, which is exhausted through the multi-stage
fluidized-bed reactor unit and is divided.
28. The apparatus for manufacturing molten iron as claimed in claim 27,
wherein the reformed exhaust gas supply tube includes a compressor for
compressing the exhaust gas, which is exhausted through the multi-stage
fluidized-bed reactor unit and which is divided, and that the tar remover is
mounted on a front end of the compressor.
29. The apparatus for manufacturing molten iron as claimed in claim 25,
wherein a cyclone, which charges dust exhausted from the melter-gasifier to the
melter-gasifier, is provided to the melter-gasifier, and the reformed-exhaust-gas
supply tube is connected to a front end of the cyclone.
30. The apparatus for manufacturing molten iron as claimed in claim 29,
wherein a transportation gas tube, which divides the reformed exhaust gas from
which CO2 is removed and which supplies the reformed exhaust gas to the
melter-gasifier as carrier gas for transporting dust separated in the cyclone, is
connected to the rear end of the cyclone.
31. The apparatus for manufacturing molten iron as claimed in claim 25,
wherein the multistage fluidized-bed reactor unit comprises:
a first preheating reactor which preheats the iron-containing mixture at a
temperature of 400 to 500°C;

a second preheating reactor which is connected to the first preheating
reactor and which re-preheats the preheated iron-containing mixture at a
temperature of 600 to 700°C;
a pre-reducing reactor which is connected to the second preheating
reactor and which pre-reduces the re-preheated iron-containing mixture at a
temperature of 700 to 800°C; and
a final reducing reactor which is connected to the pre-reducing reactor and
which finally reduces the pre-reduced iron-containing mixture at a temperature of
770 to 850°C.
32. The apparatus for manufacturing molten iron as claimed in claim 31,
wherein oxygen burners are disposed between the second pre-heating furnace
and the pre-reducing reactor and between the pre-reducing furnace and the final
reducing reactor, and supply the reducing coal gas to each of the second pre-
heating reactor and the prereducing reactor after heating the reducing coal gas.
33. The apparatus for manufacturing molten iron as claimed in claim 31,
wherein the reducing-coal-gas supply tube is connected to the final reducing
reactor.
34. The apparatus for manufacturing molten iron as claimed in claim 25,
comprising a purging-coal-gas supply tube for purging the multi-state fluidized-
bed reactor unit by dividing the reformed exhaust gas flow from which CO2 is
removed and by supplying the reformed exhaust gas to each of the fluidized-bed
reactors.
35. The apparatus for manufacturing molten iron as claimed in claim 25,
comprising an exhaust-gas-bypassing circulation tube which is connected to the
multi-stage fluidized-bed reactor unit and which supplies the total amount of
exhaust gas exhausted from the multi-stage fluidized-bed reactor unit to the
multi-stage fluidized bed reactor unit.
36. The apparatus for manufacturing molten iron as claimed in claim 25,
comprising a coal gas re-supplying tube which divides reformed exhaust gas flow
from which CO2 is removed and supplies it into the melter-gasifier together with
oxygen during the time of supplying oxygen thereto.
37. An integrated steel mill comprising:
an apparatus for manufacturing molten iron as claimed in claim 25,
an apparatus for manufacturing steel, which is connected to the apparatus
for manufacturing molten iron and which manufactures molten steel by removing
impurities and carbon from the molten iron;
a thin slab casting machine which is connected to the apparatus for
manufacturing steel and which continuously casts the molten steel supplied from
the apparatus into thin slab;
a hot-rolling machine which is connected to the thin slab casting machine
and which manufactures hot-rolled plate by hot-rolling the thin slab discharged
from the thin slab casting machine.
38. The integrated steel mill as claimed in claim 37, wherein the apparatus for
manufacturing steel comprises:
a molten-iron pre-treating apparatus which is connected to the apparatus
for manufacturing molten iron and which removes phosphorus and sulfur
contained in the molten iron discharged form the apparatus;
a decarbonization apparatus which is connected to the molten iron
pretreating apparatus and which removes carbon and impurities contained in the
molten iron discharged from the molten iron pre-treating apparatus; and
a ladle which is connected to the decarbonization apparatus and which
manufactures molten steel by refining again the molten iron discharged from the
decarbonization apparatus.
39. The integrated steel mill as claimed in claim 25, comprising a second
multi-stage fluidized-bed reactor unit which divides reformed discharged gas
from which CO2 is removed and which converts fine iron-containing ores to a
reduced material; and a second briquette-manufacturing apparatus which is
connected to the first multi-stage fluidized-bed reactor unit and which
manufactures briquettes by briquetting the reduced material at a high
temperature;
wherein the second briquette-manufacturing apparatus supplies the
reduced iron briquettes to a decarbonization-apparatus.
40. The integrated steel mill as claimed in claim 39, wherein the second multi-
stage fluidized-bed reactor unit comprises:
a preheating reactor for preheating the fine iron-containing ores at a
temperature of 600 to 700°C;
a pre-reducing reactor which is connected to the pre-heating reactor and
pre-reduces the preheated fine iron-containing ores at a temperature of 700 to
800°C; and
a final reducing reactor which is connected to the pre-reducing reactor and
finally reduces the pre-reduced fine iron-containing ores at a temperature of 770
to 850°C.


Provided is an apparatus for manufacturing molten iron using directly fine or lump
coals and fine iron-containing ores, a method thereof, an integrated steel mill using
the same, and a method thereof. The method of manufacturing the molten iron
comprises the steps of : manufacturing iron-containing mixture by mixing fine iron-
containing ores and supplementary raw materials and by drying the resultant
mixture, converting the iron-containing mixture to a reduced material by reducing and
sintering while passing the iron-containing mixture through multi-stage fluidized-bed
reactor unit, which are sequentially connected to each other, manufacturing
briquettes by briquetting the reduced material at high temperature, forming a coal
packed bed by charging lump coals and briquettes which are made by briquetting
fine coals, into a melter-gasifier as heat sources for melting the briquettes,
manufacturing molten iron by charging the briquettes into the melter-gasifier
connected to the multi-stage fuidized-bed reactor unit and by supplying oxygen into
the melter-gasifier, and supplying reducing coal-gas exhausted from the melter-
gasifier into the multi-stage fluidized-bed reactor unit.

Documents:

441-kolnp-2006-abstract-1.1.pdf

441-kolnp-2006-abstract-1.2.pdf

441-kolnp-2006-abstract.pdf

441-kolnp-2006-assignment.pdf

441-kolnp-2006-cancelled docoment.pdf

441-kolnp-2006-claims-1.1.pdf

441-kolnp-2006-claims.pdf

441-kolnp-2006-correspondence.pdf

441-kolnp-2006-description (complete).pdf

441-kolnp-2006-description complate-1.1.pdf

441-kolnp-2006-drawings-1.1.pdf

441-kolnp-2006-drawings.pdf

441-kolnp-2006-examination report.pdf

441-kolnp-2006-form 1-1.1.pdf

441-kolnp-2006-form 1.pdf

441-kolnp-2006-form 18.pdf

441-KOLNP-2006-FORM 27.pdf

441-kolnp-2006-form 3-1.1.pdf

441-kolnp-2006-form 3.pdf

441-kolnp-2006-form 5.pdf

441-KOLNP-2006-FORM-27.pdf

441-kolnp-2006-gpa.pdf

441-kolnp-2006-granted-abstract.pdf

441-kolnp-2006-granted-assignment.pdf

441-kolnp-2006-granted-claims.pdf

441-kolnp-2006-granted-correspondence.pdf

441-kolnp-2006-granted-description (complete).pdf

441-kolnp-2006-granted-drawings.pdf

441-kolnp-2006-granted-examination report.pdf

441-kolnp-2006-granted-form 1.pdf

441-kolnp-2006-granted-form 18.pdf

441-kolnp-2006-granted-form 3.pdf

441-kolnp-2006-granted-form 5.pdf

441-kolnp-2006-granted-gpa.pdf

441-kolnp-2006-granted-pa.pdf

441-kolnp-2006-granted-reply to examination report.pdf

441-kolnp-2006-granted-specification.pdf

441-kolnp-2006-granted-translated copy of priority document.pdf

441-kolnp-2006-intenational publication.pdf

441-kolnp-2006-international search report.pdf

441-kolnp-2006-others.pdf

441-kolnp-2006-pa.pdf

441-kolnp-2006-petition under rule 137.pdf

441-kolnp-2006-reply to examination report-1.1.pdf

441-kolnp-2006-reply to examination report-1.2.pdf

441-kolnp-2006-reply to examination report.pdf

441-kolnp-2006-specification.pdf

441-kolnp-2006-translated copy of priority document.pdf


Patent Number 238884
Indian Patent Application Number 441/KOLNP/2006
PG Journal Number 09/2010
Publication Date 26-Feb-2010
Grant Date 24-Feb-2010
Date of Filing 27-Feb-2006
Name of Patentee POSCO
Applicant Address 1 GOEDONG-DONG, NAM-KU, POHANG-SHI, KYUNGSANGBUK-DO
Inventors:
# Inventor's Name Inventor's Address
1 KIM DEUK CHAE POSCO 5, DONGCHON-DONG, NAM-KU, POHANG-SHI, KYUNGSANGBUK-DO 790-360
2 SCHENK JOHANNES TURMSTRASSE 44, A-4031 LINZ
3 SCHMIDT MARTIN TURMSTRASSE 44, A-4031 LINZ
4 WIEDER KURT TURMSTRASSE 44, A-4031 LINZ
5 WURM JOHANN TURMSTRASSE 44, A-4031 LINZ
6 ZEHETBAUER KARL TURMSTRASSE 44, A-4031 LINZ
7 KANG CHANG OH 1 GOEDONG-DONG, NAM-KU, POHANG-SHI, KYUNGSANGBUK-DO 790-300
8 LEE HOO GEUN POSCO 5, DONGCHON-DONG, NAM-KU, POHANG-SHI, KYUNGSANGBUK-DO 790-360
9 JOO SANG HOON POSCO 5, DONGCHON-DONG, NAM-KU, POHANG-SHI, KYUNGSANGBUK-DO 790-360
10 SHIN MYOUNG KYUN POSCO 5, DONGCHON-DONG, NAM-KU, POHANG-SHI, KYUNGSANGBUK-DO 790-360
11 KIM JIN TAE POSCO 5, DONGCHON-DONG, NAM-KU, POHANG-SHI, KYUNGSANGBUK-DO 790-360
12 LEE GU POSCO 5, DONGCHON-DONG, NAM-KU, POHANG-SHI, KYUNGSANGBUK-DO 790-360
13 KIM SANG HYUN POSCO 5, DONGCHON-DONG, NAM-KU, POHANG-SHI, KYUNGSANGBUK-DO 790-360
14 KIM WAN GI POSCO 5, DONGCHON-DONG, NAM-KU, POHANG-SHI, KYUNGSANGBUK-DO 790-360
15 EDER THOMAS TURMSTRASSE 44, A-4031 LINZ
16 HAUZENBERGER FRANZ TURMSTRASSE 44, A-4031 LINZ
17 MILLNER ROBERT TURMSTRASSE 44, A-4031 LINZ
PCT International Classification Number C21B 3/00
PCT International Application Number PCT/KR2004/003192
PCT International Filing date 2004-12-06
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10-2004-0101147 2004-12-03 Republic of Korea
2 10-2003-0088033 2003-12-05 Republic of Korea
3 10-2003-0088035 2003-12-05 Republic of Korea