[Technical Field]
The present invention relates to a method and an apparatus for
immobilizing carbon dioxide, and more particularly, to a method of immobilizing
carbon dioxide and manufacturing a metal carbonate by reacting steel mi
waste with a strong acid to form metal ions, and then reacting the metal ions
with alkali waste water together with carbon dioxide.
[Background Art]
In an integrated iron and steel making process, carbon dioxide makes up a large amount of total emissions generated therefrom, and particularly, about 90 % or more of generated emissions is carbon dioxide, such that much
research for treating carbon dioxide has been conducted.
First, existing CCS (carbon dioxide capture and storage) has a problem
in that a storage space such as mahne storage or underground storage should
be ensured in order to collect carbon dioxide and store it.
In the steelworks, when steel products are produced, iron and steel
sludge and dust are additionally generated, and it is expensive to treat them.
Generally, examples of suppressing discharge of carbon dioxide include
a method of reducing use of fossil fuels, and a method of separating and
collecting carbon dioxide to immobilize it.
Particularly, the latter method Is a method of separating and collecting

carbon dioxide to use as a raw material for methanol synthesis, or is a method
of separating and collecting carbon dioxide and then disposing of carbon
dioxide in the sea or immobilizing it as a carbonate.
Meanwhile, examples of slag generated in a steelmaking process of the
steelworks include molten iron pretreatment slag, steel converter slag, stainless
slag, electric furnace slag, and the like, and these steelmaking slags are
partially used as a cement aggregate or as an aggregate for road and civil
construction, but the remainder is mostly buried. However, securing of landfills
is gradually becoming more difficult and there is a limitation in use methods up
to now, and thus various methods for using the discarded slag have been
proposed.
However, if the steel mill waste such as the sludge or the dust
generated in the iron and steel making process is used, an amount of the
discarded steel mill waste may be reduced to reduce disposal cost thereof, and
if carbon dioxide is immobilized by using the steel mill waste, environmental
pollution may be prevented, such that there is a demand for research thereof.
The above information disclosed in this Background section is only for
enhancement of understanding of the background of the invention and therefore
it may contain information that does not form the prior art that is already known
in this country to a person of ordinary skill in the art.
[DISCLOSURE]
[Technical Problem]
The present Invention has been made in an effort to provide a method of

immobilizing carbon dioxide and manufacturing a metal carbonate by reacting carbon dioxide with alkali waste water to form a carbonate, and substituting a
metal salt into the carbonate.
[Technical Solution]
An exemplary embodiment or a plurality of exemplary embodiments of the present invention provide a method of immobilizing carbon dioxide,
including; providing a steel mill waste; concentrating the steel mill waste;
dehydrating the concentrated steel mill waste; separating hydrogen and a
precipitate formed by mixing and agitating the dehydrated steel mill waste and a
strong acid; injecting an exhaust gas including alkali waste water and carbon
dioxide into the separated precipitate to manufacture a carbonate, and then
manufacturing a metal carbonate (FeCOa) by a substitution reaction of the
carbonate and the precipitate; and drying the metal carbonate (FeCOa).
The steel mill waste includes a waste sludge or dust generated in an iron and steel making process, and the precipitate includes FeCla and FeCIa generated by a reaction of the steel mill waste and hydrochloric acid (HCI).
The alkali waste water may include one or more of NH3, CaO, and
NaOH generated in the iron and steel making process, and the carbonate may
2-
be one or more of HCO3", CO3 , and NH2CO2".
2+
The metal carbonate (FeCOs) is formed by a reaction of iron ions (Fe )
generated by the precipitate and the carbonate, and an iron content (total Fe) of
the steel mill waste is 40 to 60 wt%.
The method may further include concentrating the metal carbonate
before the drying, and dehydrating the concentrated metal carbonate.

The metal carbonate may be supplied to a blast furnace or a melter-
gasifier to be used as a core activating agent, metal carbonate supplied to the
blast furnace or the melter-gasifier is decomposed into iron oxide (FeO) and
carbon dioxide, and decomposed carbon dioxide is reacted with pulverized coa
to generate a reduction gas.
The metal carbonate is blown through a dust burner of the melter-
gasifier, or is blown through a tuyere into the blast furnace.
In this case, a pH of the strong acid is 1 or less, and a pH of the alkali
waste water is 10 or more.
The exhaust gas including carbon dioxide is one or more of a BFG (blast
furnace gas), a FOG (FINEX off gas), or a COG (coke oven gas) generated in
an iron and steel making process, and the hydrogen is used as a reduction gas
of a fluidized-bed reduction furnace.
Another exemplary embodiment of the present invention provides an apparatus for immobilizing carbon dioxide, including: a concentration apparatus
concentrating a steel mill waste; a dehydration apparatus dehydrating the
concentrated steel mill waste; a melt apparatus reacting the dehydrated steel
mill waste and a strong acid to generate hydrogen and a metal salt; a mixing
and agitation apparatus reacting the metal salt with an exhaust gas containing
carbon dioxide and alkali waste water to manufacture a metal carbonate; and a
drying apparatus drying the metal carbonate.
The mixing and agitation apparatus includes at least one mat dipped in
the mixing and agitation apparatus and supplying the metal salt and the exhaust
gas including carbon dioxide to the alkali waste water.

The dehydration apparatus is a filter press, and a suction apparatus
sucking metal carbonate precipitated in the mixing and agitation apparatus is
connected to the drying apparatus to supply the precipitated metal carbonate to
the drying apparatus.
The apparatus may further include a concentrator concentrating the
metal carbonate between the suction apparatus and the drying apparatus, and
a dehydrator formed between the concentrator and the drying apparatus to
dehydrate the concentrated metal carbonate.
The melt apparatus may include: a strong acid storage tank storing the
strong acid; a melt cell in which the strong acid and the steel mill waste are
reacted; and an agitator agitating a solution in the melt cell.
The melt apparatus may further include a check valve adjusting an
amount of the strong acid, and the melt apparatus may further include a


hydrogen storage tank storing hydrogen generated by a reaction of the steel m

waste and the strong acid.
[Advantageous Effects]
According to the exemplary embodiments of the present invention, it is
possible to remove a large amount of carbon dioxide generated in an iron and
steel making process at a low cost by using waste resources in the process.
Further, it is possible to manufacture a metal carbonate subjected to
neutralization treatment by simultaneously injecting carbon dioxide and metal
ions into alkali waste water generated in the iron and steel making process, and
it is possible to activate a core by using metal carbonate as a comburent
[Description of the Drawings]

FIG. 1 is a flowchart of a method of immobilizing carbon dioxide of an
exemplary embodiment according to the present invention.
FIG. 2 is a schematic diagram of an apparatus for immobilizing carbon dioxide of the exemplary embodiment according to the present invention.
FIG. 3 schematically illustrates a melting apparatus and a mixing and
agitation apparatus of a constitution of FIG. 2.
FIG. 4 schematically illustrates a shape of a tuyere of a general blast
furnace
[Mode for Invention]
Advantages and features of the present invention and methods to achieve them will be elucidated from exemplary embodiments described below
in detail with reference to the accompanying drawings. However, exemplary
embodiments introduced herein are provided to make disclosed contents
thorough and complete and sufficiently transfer the spirit of the present invention to those skilled in the art. Therefore, the present invention will be defined only by the scope of the appended claims. Like reference numerals
designate like elements throughout the specification.
An exemplary embodiment according to the present invention relates to a method and an apparatus for immobilizing carbon dioxide, in which waste
sludge and dust containing an iron (Fe) component that is a steel mill waste are used to immobilize carbon dioxide generated in an iron and steel making process and manufacture a metal carbonate (FeCOa), and the metal carbonate
is supplied to a blast furnace or a FINEX melter-gasifier to activate a core.
FIG. 1 illustrates the order of immobilization of carbon dioxide according

to the exemplary embodiment of the present invention, and hereinafter, the
method of immobilizing carbon dioxide by using the steel mill waste will be
described with reference to FIG. 1.
First, in the exemplary embodiment according to the present invention.
the waste sludge and the dust that are the steel mill waste generated in the iron
and steel making process are provided (S100) to be concentrated by a
concentration apparatus (S110), and then the concentrated steel mill waste is
dehydrated by using a dehydration apparatus such as filter press (S120).
Thereafter, the dehydrated steel mill waste and a strong acid are mixed and
agitated (S130) to form hydrogen and a precipitate.
In order to use the hydrogen and the precipitate for separate purposes,
the hydrogen and the precipitate are separated (S140), the hydrogen is used as
a reduction gas in a fluidized-reduction furnace and the like, and the precipitate
is used to generate a metal carbonate.
In the exemplary embodiment according to the present invention, the
waste sludge includes all sludges generated in the iron and steel making
process including ironmaking and steelmaking processes.
In this case, the precipitate is FeC^ and FeCIs formed by reacting the waste sludge or the dust containing iron with the strong acid such as hydrochloric acid (HCI).
Thereafter, FeCl2 and FeCb are dissolved in water in an agitator in a melt apparatus to exist as Fe^"*" and Fe^"".
That is, when the steel mill waste is reacted with the hydrochloric acid,

3+
2+
divalent iron becomes Fe and ferric oxide (Fe203) becomes Fe . Hydrogen

2+ I r-«3+
generated in a precipitation reaction with the iron ions (Fe and Fe ) is
separated, and the separated precipitate is reacted with a carbonate
The carbonate is formed by mixing alkali waste water and carbon
dioxide, and the precipitate is injected into the carbonate to manufacture a
metal carbonate (FeCOs) (S150). In the exemplary embodiment according to
the present invention, the metal carbonate (FeCOa) is dried (S180) in order to
use the generated metal carbonate as a comburent in the blast furnace or the
melter-gasifier.
In this case, before the metal carbonate is dried, the metal carbonate
may be subjected to a concentration process (S160) and a dehydration process
(S170).
Hereinafter, the aforementioned processes will be more specifically
described.
FIG. 2 illustrates a schematic diagram of the apparatus for immobilizing
carbon dioxide of the exemplary embodiment according to the present invention.
and hereinafter, the apparatus will be described with reference to FIG. 2.
Generally, the steel mill waste that is a byproduct of steelworks, such as
the waste sludge or the dust, and generated in the iron and steel making
process, is embedded or discharged to the outside to be treated, and includes
2+ -7„2+ I A„2+
metal salts such as Fe , Zn , and Ag . In the exemplary embodiment

2+
according to the present invention, the Fe is reacted with a carbonate to
manufacture FeCOs that is a metal carbonate.
2+
For this purpose, first, a manufacturing process of the iron ion (Fe ) is
performed.

Iron oxide such as Fe203, Fe304, or FeO is included in steel mill waste
20 of a steelworks 10, such as the waste sludge or the dust, and is reacted with
the strong acid, particularly the hydrochloric acid, to form iron chloride.
Before the iron chloride is formed, the steel mill waste 20 is concentrated and dehydrated by using a concentration apparatus 100 and a dehydration apparatus 110. In this case, moisture of the steel mill waste may
not be completely removed, and in the exemplary embodiment according to the
present invention, a filter press is used as the dehydration apparatus. Thereby
moisture is sufficiently removed to cause a good reaction with the strong acid.
The filter press is apparent to a person of ordinary skill in the art to which the
present invention pertains, and thus a specific description thereof will be omitted
In this case, the iron chloride is formed by the following reaction
equation. This is a dissociation reaction of FeaOa, Fe304, and FeO included in
the steel mill waste. For the dissociation reaction, in the exemplary
embodiment according to the present invention, the hydrochloric acid (HCI) that
is the strong acid is added to the steel mill waste 20 into a melt apparatus 200
Fe + 2HCI -^ FeCU + H
Fe203 + 6HC! -^ 2FeCl3 + SHsO
FeaOs + Fe + 6HCI -> 3 FeCl2 + SHaO
Fe304 + 8HCI -> FeCl2 + 2FeCl3 + 3H2O
FeO + 2HCI ^ FeCl2 + H2O
In the aforementioned reaction equations, the pH of the hydrochloric
acid is 1 or less.
In this case, a material having a size of 100 pm or less is used as the

steel mill waste 20 such as the waste sludge or the dust. If a particle size of
the steel mill waste 20 is more than 100 |jm, since a reaction surface area of the
iron oxide is not sufficient, the dissociation reaction is not performed well, and
thus in the exemplary embodiment according to the present invention, the size
of the steel mill waste 20 is limited to 100 |jm or less. However, the particle
size of the steel mill waste may be changed according to a generated
environment, and in the case where the steel mill waste is generated in the
FINEX melter-gasifier, the particle size may be 30 (jm or less.
FeCl2 and FeCIa formed by the aforementioned reaction equations are easily dissolved by water to exist as Fe^"*" and Fe^"*^. In this case, as seen from
the aforementioned reaction equations, hydrogen gas may be generated, and
as described above, the generated hydrogen gas having high puhty may be
used as a reduction gas in a fluidized-bed reduction furnace of a FINEX iron
making process and the like.
As described above, in order to form iron chloride, in the exemplary
embodiment according to the present invention, the steel mill waste having an
iron content (total Fe) of 40 to 60 weight percent (wt%) is used. If the iron
content is less than 40 %, since an amount of the discarded steel mill waste is
arger than an amount of a comburent to be manufactured as will be described
later, manufacturing efficiency of the comburent is reduced. Further, if the iron
content is more than 60 %, efficiency of the comburent is increased, but if the
iron content is more than 60 %, since the steel mill waste may be usefully used
in the iron and steel making process, in the exemplary embodiment according to
the present invention, the iron content in the steel mill waste is limited to the

aforementioned range.
As described above, manufactured FeCb and FeCIs are dissolved in water to exist in a metal ion form such as Fe^"" and Fe^"" and be reacted with the
carbonate and thus manufacture the metal carbonate (FeCOa).
Hereinafter, a process of manufacturing carbonate of the exemplary
embodiment according to the present invention will be described.
n the exemplary embodiment according to the present invention,
carbonate is manufactured by reacting alkali waste water discharged in the iron
and steel making process and carbon dioxide. That is, NH3, CaO, or NaOH is
included in waste water discharged in the iron and steel making process, and
one or more thereof and carbon dioxide are reacted to form various kinds of
carbonates. Each reaction equation is the same as the following equation.
First, the reaction equation relating to NH3 is as follows. A carbonate
2-
such as HCO3, CO3 , or NH2CO2" is generated by the following reaction
equation.
NH3 + CO2 + H2O <-^> NH/ + HCO3
NH3 + HC03"<~> C03^" + 2NH/
NH3 + HC03"<-> NH2CO2" + H2O
The reaction equation of CaO of alkali waste water is as follows, and in

2-
this case, generated carbonates are HCO3" and CO3 .
CaO(s) + H20-^ Ca (0H)2
2+
Ca (OH)2(s) -^ Ca^^(aq) + 20H-(aq)
C02(aq) + OHXaq) -^ HC03"(aq)
2-
HC03"(aq) + OH"(aq) -^ H2O + C03^"(aq)

2~
Further, in the case of NaOH, CO3 ions are generated by the following
reaction.
NaOH(s) + H20(l) ^ Na(aq) + OH"(aq) + HjOCI)

2-
OH^ + CO2 ^ COs^" + H2O

While the reaction of alkali waste water and carbon dioxide very rapidly
occurs at an interface of a gas/liquid, carbon dioxide is collected. In the exemplary embodiment according to the present invention, an exhaust gas including carbon dioxide includes one or more of a BFG (blast furnace gas), a
FOG (FINEX off gas), or a COG (coke oven gas) generated in the iron and steel
making process.
The pH of alkali waste water may be 10 or more. In the case where the
pH is less than 10, an ability of immobilizing carbon dioxide is reduced. That is,
since a neutralization ability of carbon dioxide that is an acid gas is reduced, in
the exemplary embodiment according to the present invention, the pH of alkali
waste water is limited to 10 or more
For example, in the case where the pH of alkali waste water is 11, alkali
waste water is reacted with CO2 that is the acid gas to neutralize the pH of alkali
waste water to 7 to 8. That is, as the pH of alkali waste water is increased, a
chance of actively performing the reaction with CO2 is increased. Accordingly,
in the exemplary embodiment according to the present invention, the pH of
alkali waste water is limited to 10 or more.
A carbonate (HCO3", CO3 , or NH2CO2") formed by the aforementioned reaction is reacted with Fe^"" in a mixing and agitation apparatus 300 to form a
metal carbonate.

That is, as shown in FIG. 2, carbon dioxide and alkali waste water that
are byproducts of the iron and steel making process of a steelworks 10 are
received to manufacture a carbonate from a reaction thereof and react the
manufactured carbonate and the iron ion and thus form the metal carbonate
(FeCOa).
n this case, the reaction equation is the same as the following equation

2+
Fe^ + 2HCO3" <-> CO2 + FeCOa + H2O

2+ . r^r\ 2-
Fe^" + COs^" ^ FeCOa

Fe^^ + NH2C02" + H2O ^ FeCOa + NH/
As in the aforementioned reaction equation, the carbonate is transferred
from the interface to precipitate a thermodynamically stable metal salt (FeCOa)
and immobilize CO2.
Thereafter, the metal carbonate is precipitated in the mixing and agitation apparatus 300. In the exemplary embodiment according to the
present invention, in order to use the metal carbonate as the comburent, the
metal carbonate is dried by using a drying apparatus 400, and in the exemplary
embodiment according to the present invention, drying may be easily performed
through the concentration and dehydration processes by using a concentrator
370 and a dehydrator 390 before drying.
The comburent is supplied to a pulverized coal blowing lance (PCI) of a
blast furnace 600 and a melter-gasifier 500 to promote complete combustion in
a raceway and prevent generation of an uncombusted carbon portion. The
comburent may be used as a core activating agent for an activation operation of
a core portion, and particularly may be used for an early heat increase of the

core portion in order to increase the degree of operation in early stages after
furnace maintenance.
Generally, in a blast furnace operation, PCI is performed through a blast
furnace tuyere in order to make a high tapping operation possible by reducing a
use amount of a costly coke and further filling iron ore in a reduced coke space.
In this case, for thermal stability of a furnace lower portion, the metal salt of the
blast furnace sludge and the iron and steel making dust that are steel mill waste
resources is added together with FeCOa immobilizing CO2 to be injected, and
FeCOs is decomposed into FeO and CO2 at 400 to 550 °C.
n this case, in a decomposition process, energy of about 1015 kJ/kg is
consumed, a temperature of a combustion region of the tuyere through which PCI (pulverized coal injection) into the blast furnace is performed is about 1250 °C, energy is supplied by a hot wind to cause the following decomposition
reaction, and generated FeO is reduced into Fe by direct reduction
FeCOs <■> FeO + CO2
FeO + C ^ Fe + CO
n this case, generated CO2 is reacted with pulverized coal around the
raceway to perform the following reaction. In this case, the temperature is
about 950 °C to 2200 °C, and the reaction equation is as follows.
CO2 + C <> 2C0 AH= +173kJ/mole
Accordingly, if FeCOs is added in the combustion region to be used,
sufficient CO is generated, and generated carbon monoxide ascends over a
furnace (shaft) to reduce a charged material descending on the furnace-
Further, FeCOa can be blown through a dust burner on the melter-

gasifier into the melter-gasifier to be reused. The dust burner supplies
additional oxygen in addition to oxygen required in dust combustion in order to
prevent deterioration of the temperature in the melter-gasifier The additional
oxygen is supplied to combust a portion of the reduction gas formed in a dome
portion of the melter-gasifier and thus prevent deterioration of the temperature.
Hereinafter, the process of immobilizing carbon dioxide of the exemplary
embodiment according to the present invention will be more specifically
described
FIG. 3 illustrates an apparatus for immobilizing carbon dioxide in the
exemplary embodiment according to the present invention, and the apparatus
includes a melt apparatus and a mixing and agitation apparatus
Referring to FIG. 3, the steel mill waste such as the waste sludge or the
dust that is the byproduct generated in the iron and steel making process is
concentrated by the concentration apparatus 100, and the concentrated steel
mill waste is dehydrated by the dehydration apparatus 110 to remove moisture
of the steel mill waste.
The dehydrated steel mill waste is transported to a melt cell 230 of the
melt apparatus 200, a strong acid solution stored in a strong acid storage tank
210 is moved to the melt cell 230 by adjustment of a check valve 220, and if the steel mill waste and the strong acid solution are mixed and agitated by an
agitator 240, the metal salt is generated.
The metal salt is FeCb and FeCb, and the metal salt is dissolved in water to exist in a state of Fe^^ and Fe^"" and thus form a precipitate 235. In
this case, hydrogen may be formed while the metal salt is formed, and since the

hydrogen has high purity, it is stored in a hydrogen storage tank 250 to be used
in a process of reducing iron ore by the hydrogen gas and the like.
The metal salt is injected through a metal ion injection pipe 310 into the mixing and agitation apparatus 300, and particularly, Fe^"" is reacted with the
carbonate to form the metal carbonate 337. The carbonate is formed by the
reaction of the exhaust gas including carbon dioxide injected from an external
carbon dioxide injection pipe 320 and alkali waste water 330 stored in a waste
water storage tank 335, and the exhaust gas and alkali waste water 330 are
reacted in the mixing and agitation apparatus 300.
n the exemplary embodiment according to the present invention, the
2+
Fe is injected together with the exhaust gas including the carbon dioxide into
2+
the mixing and agitation apparatus 300, and the injected iron ions (Fe ) and
exhaust gas are uniformly supplied and dispersed through at least one mat 340
having a plurality of gas diffuser hoses into the alkali waste water 330.
Carbon dioxide uniformly dispersed from the mat 340 is reacted with
NH3, CaO, or NaOH existing in the alkali waste water 330 to form a carbonate
2-
such as HCO3", CO3 , and NH2CO2". In this case, the pH is checked by a pH
electrode 350 to maintain the pH in the mixing and agitation apparatus 300 at
10 or more
2+
The carbonate and the iron ion (Fe ) are reacted in the mixing and
agitation apparatus 300 to form the metal carbonate (FeCOs) 337. The metal
carbonate 337 sinks to the bottom of the mixing and agitation apparatus 300 as
time passes to exist as the precipitate.
Since the metal carbonate 337 may be used as the comburent through a

metal carbonate injection pipe 420 in the blast furnace 600 or the melter-gasifier
500, in the exemplary embodiment according to the present invention, the metal
carbonate 337 should be dried. The metal carbonate 337 may be subjected to
concentration and dehydration steps as steps prior to drying. That is, in FIG. 3,
in order to supply metal carbonate 337 to the drying apparatus 400, precipitated metal carbonate is sucked using a suction apparatus 360 and then supplied
through a metal carbonate transportation pipe 365 to the drying apparatus 400
and in order to improve manufacturing efficiency of the comburent before meta
carbonate is supplied to the drying apparatus 400, the metal carbonate may be
subjected to concentration and dehydration and then supplied to the drying
apparatus 400.
n this case, drying is sufficient even if the metal carbonate is not dried
enough to completely remove moisture but is dhed enough to be supplied to the
dust burner 520 of the blast furnace 600 or the melter-gasifier 500 and thus be
used as the comburent.
FIG. 4 schematically illustrates a shape of a tuyere 620 in a general
blast furnace 600, the tuyere 620 is formed through a furnace wall 610 of the
blast furnace, and when oxygen is supplied through a blowing pipe 640 and
simultaneously pulverized coal 655 is subsidiarily blown through a pulverized
coal blowing lance (PCI lance) 650, the metal carbonate is added together to be
injected.
The metal carbonate 337 causes a decomposition reaction around a
raceway 630 by a hot wind at a high temperature, and FeO generated by the
decomposition reaction is reduced into Fe by a direct reduction method.

Carbon monoxide is generated while reduction into Fe occurs, and
carbon monoxide reduces charged iron ore.
Although the exemplary embodiments of the present invention have
been described with reference to the accompanying drawings, it will be
apparent to those skilled in the art that various modifications and changes may
be made thereto without departing from the technical spirit or essential feature
of the invention.
Therefore, the aforementioned embodiments should be understood to
be exemplary but not limitative in all aspects. The scope of the present
invention is represented by the claims as described later rather than the
detailed description, and it is to be construed that all modifications and modified
embodiments deduced from the meaning and the scope of the claims, and the
concepts equivalent thereto, are included within the scope of the present
invention.

WE CLAIMS:-
A method of immobilizing carbon dioxide, comprising:
providing a steel mill waste;
concentrating the steel mill waste;
dehydrating the concentrated steel mill waste;
separating hydrogen and a precipitate formed by mixing and agitating
the dehydrated steel mill waste and a strong acid;
injecting an exhaust gas including alkali waste water and carbon dioxide
into the separated precipitate to manufacture a carbonate, and then
manufacturing a metal carbonate (FeCOa) by a substitution reaction of the
carbonate and the precipitate; and
drying the metal carbonate (FeCOs)
[Claim 2]
The method of claim 1, wherein the steel mill waste includes a waste
sludge or dust generated in an iron and steel making process
[Claim 3]
The method of claim 1, wherein the strong acid is hydrochloric acid
(HCI), and the precipitate includes FeCl2 and FeCIs generated by a reaction of
the steel mill waste and the hydrochloric acid (HCI).
[Claim 4]
The method of claim 1, wherein the alkali waste water includes one or
more of NH3, CaO, and NaOH generated in the iron and steel making process.

[Claim 5]
The method of claim 4, wherein the carbonate is one or more of HCO3",
C03^, and NH2CO2".
[Claim 6]
The method of claim 1, wherein the metal carbonate (FeCOa) is formed
2+
by a reaction of iron ions (Fe ) generated by the precipitate and the carbonate.
[Claim 7]
The method of claim 1, wherein an iron content (total Fe) of the steel mill
waste is 40 to 60 wt%.
[Claim 8]
The method of claim 1, further comprising:
concentrating the metal carbonate before the drying; and
dehydrating the concentrated metal carbonate.
[Claim 9]
The method of claim 1, wherein the metal carbonate is supplied to a
blast furnace or a melter-gasifier to be used as a core activating agent.
[Claim 10]
The method of claim 9, wherein the metal carbonate supplied to the
blast furnace or the melter-gasifier is decomposed into iron oxide (FeO) and
carbon dioxide, and decomposed carbon dioxide is reacted with pulverized coa
to generate a reduction gas
[Claim 11]
The method of claim 9, wherein the metal carbonate is blown through a

dust burner of the melter-gasifier
[Claim 121
The method of claim 9, wherein the metal carbonate is blown through a
tuyere to the blast furnace
[Claim 131
The method of claim 1, wherein a pH of the strong acid is 1 or less.
[Claim 141
The method of claim 1, wherein a pH of the alkali waste water is 10 or
more.
[Claim 151
The method of claim 1, wherein the exhaust gas including carbon
dioxide includes one or more of a BFG (blast furnace gas), a FOG (FINEX off
gas), or a COG (coke oven gas) generated in an iron and steel making process.
[Claim 161
The method of claim 1, wherein the hydrogen is used as a reduction gas
of a fluidized-bed reduction furnace.
[Claim 171
An apparatus for immobilizing carbon dioxide, comprising:
a concentration apparatus concentrating a steel mill waste;
a dehydration apparatus dehydrating the concentrated steel mill waste;
a melt apparatus reacting the dehydrated steel mill waste and a strong
acid to generate hydrogen and a metal salt;
a mixing and agitation apparatus reacting the metal salt with an exhaust

gas containing carbon dioxide and alkali waste water to manufacture a metal
carbonate; and
a drying apparatus drying the metal carbonate
[Claim 18]
The apparatus of claim 17, wherein the mixing and agitation apparatus
includes at least one mat dipped in the mixing and agitation apparatus and
supplying the metal salt and the exhaust gas including carbon dioxide to the
alkali waste water.
[Claim 19]
The apparatus of claim 17, wherein the dehydration apparatus is a filter
press.
[Claim 20]
The apparatus of claim 17, wherein a suction apparatus sucking metal
carbonate precipitated in the mixing and agitation apparatus is connected to the
drying apparatus to supply the precipitated metal carbonate to the drying
apparatus.
[Claim 21]
The apparatus of claim 20. further comprising a concentrator
concentrating the metal carbonate between the suction apparatus and the
drying apparatus, and a dehydrator formed between the concentrator and the
drying apparatus to dehydrate the concentrated metal carbonate
[Claim 22]
The apparatus of claim 17, wherein the melt apparatus includes:

a strong acid storage tank storing the strong acid;
a melt cell in which the strong acid and the steel mill waste are reacted; and
an agitator agitating a solution in the melt cell.
tClaim 231
The apparatus of claim 22, wherein the melt apparatus further includes
a check valve adjusting an amount of the strong acid
[Claim 24]
The apparatus of claim 17, wherein the melt apparatus further includes
a hydrogen storage tank storing hydrogen generated by a reaction of the steel
mill waste and the strong acid.
[Claim 25]
The apparatus of any one of claims 17 to 24, wherein the strong acid is
hydrochloric acid (HOI).