PCT/KR2005/000218
RO/KR 25.03.2005
A METHOD FOR MANUFACTURING BRIQUETTES DIRECTLY USING
COAL WITH WIDE RANGE OF SIZE, THE METHOD USING THE SAME
AND THE APPARATUS USING THE SAME
BACKGROUND OF THE INVENTION
5 (a) Field of the Invention
The present invention relates to method for manufacturing coal
briquettes, and the method and the apparatus for manufacturing moiten irons
using the same. More particularly, the present invention relates to method
for manufacturing coal briquettes directly using coals with wide range of grain
10 size, the method and the apparatus for manufacturing molten irons using the
same.
(b) Description of the Related Art
The iron and steel industry is a core industry that supplies the basic
materials needed in construction and in the manufacture of automobiles,
15 ships, home appliances, and many of the other products we use. It is also
an industry with one of the longest histories that has progressed together
with humanity. In an iron foundry, which plays a pivotal roll in the iron and
steel industry, after molten iron (i.e., pig iron in a molten state) is produced
using iron ore and coal as raw materials, steel is produced from the molten
20 iron and is then supplied to customers.
Approximately 60% of the world's iron production is realized using
the blast furnace method developed in the 14th century. In the blast
furnace method, cokes produced using bituminous coals as raw materials,
and iron ores that have undergone a sintering process are charged into a
25 blast furnace, and oxygen gas is supplied to the furnace to reduce the iron
ore, thereby manufacturing molten iron. The blast furnace method, which is
a main aspect of molten iron production, requires raw materials having a
predetermined hardness and a grain size that can ensure permeability in the
1

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furnace. As a carbon source used as fuel and a reducing agent, cokes
made from specific raw coal are used, and as an iron source, sintered ores
which have undergone a successive compacting process have been used.
Accordingly, in the modern blast furnace method, it is necessary to include
5 raw material pre-processing equipment such as cokes manufacturing
equipment and sintering equipment to process iron ores, and not only it is
necessary to obtain accessory equipments in addition to the blast furnace,
but equipment to prevent and minimize the generation of pollution in the
accessory equipments are needed. The amount of investment, therefore, is
10 considerable and ultimately increasing manufacturing costs. In order to
solve these problems of the blast furnace method, much research is being
conducted into producing molten irons by directly using raw coals as fuels
and a reducing agent, and also directly using iron ores as iron sources.
U.S. Patent Nos. 4,409,023 and 5,534,046 both disclose an
15 apparatus and method for producing liquid molten pig iron using lump iron
sources. The apparatus for producing molten iron is realized using a
melter-gasifier that is connected to a packed bed-type reactor or a fluidized
bed-type reactor. Reduced irons emitted from the packed bed-type reactor
for the fluidized bed-type reactor are charged into the melter-gasifier to be
20 melted, after which it is converted into molten iron and slag then discharged.
Coals are supplied to the melter-gasifier to form a coal-packed bed, and
oxygen is supplied through a tuyere of a lower area of the coal-packed bed
to burn the coals. Combustion gas is converted into a hot reduced gas
while rising through the coal-packed bed. The hot reduced gas is
25 exhausted to outside the melter-gasifer and is supplied as reduced gas to
the packed bed-type reactor or fluidized bed-type reactor.
FIG. 4 is a schematic view showing performance of the above
melter-gasifier. As shown in FIG. 4, a melter-gasifier 40 to which coals and
reduced iron are supplied mainly includes a dome on an upper area thereof,
30 and a coal-packed bed in a lower area thereof.

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The coals in room temperature supplied to inside the melter-gasifier
40 directly contact a hot gas flow of approximately 1000°C in the dome so as
to be quickly heated, then descends to an upper surface of the coal-packed
bed. While moving toward a lower area of the coal-packed bed, the coal
5 passes through a primary pyrolysis region, a secondary pyrolysis region, a
gasification region, and a combustion region to be converted into a hot
reduced gas. In the primary pyrolysis region, tar and pyrolysis gas are
generated, and in the secondary pyrolysis region, char is condensed and H2
gas is generated.
10 Further, in the gasification region, chemical reactions occur as
indicated by the chemical formulae of FIG. 4. Also, reduced irons supplied
to the melter-gasifier 40 are melted to form melted pig iron, and a reaction
occurs in which ash comprised in the coal and gangue comprised in the
reduced iron are converted to slags. Heat used in the melting and slag
15 reactions is supplied by heat exchange between reduced irons and coals,
and by hot combustion gas generated through the burning of coals in the
combustion region due to the chemical reaction indicated by the chemical
formula.
In order for satisfactory performance in such a melter-gasifier, it is
20 important to form a coal-packed bed that maintains a suitable permeability.
To realize this, it is necessary to control the grain size of the coals to within a
specific range.
U.S. Patent Nos. 4,409,023 and 5,534,046 disclose limitation of the
grain size of coals in the melter-gasifier to between 8mm and 35mm.
25 However, coals used to manufacture iron supplied from various countries of
origin include significant quantities of fine coals with grain sizes of less than
8mm. Therefore, prior to charge into the melter-gasifier, it is necessary to
select and remove these coals, resulting in a loss of a substantial amount of
the raw coals. Also, this places an undue limitation on the grain size of the
30 raw coals.

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To overcome these problems, U.S. Patent No. 6,332,911 discloses a
method that uses fine coals in a melter-gasifier. In this method, among raw
material coals having the same composition and properties, lump coals
having a grain size of 8mm or more are directly charged into the melter-
5 gasifier, and fine coals with a grain size of less than 8mm are charged into
the melter-gasifier after bitumen is added as a binder to be formed into coal
briquettes of a predetermined size or greater.
With the use of this method, the raw materials of the same
composition and properties are used after undergoing sorting according to a
10 grain size. As a result, the performance in the melter-gasifier during the
manufacture of molten iron is affected by the raw coals such that much care
must be taken in selecting the raw coals, that is, selection of the raw coals is
limited. In addition, in the case of coal briquettes used in the melter-gasifier,
many conditions must be satisfied in addition to the condition of grain size to
15 maintain a suitable permeability. These include the satisfaction of the
conditions of compressive strength, hot strength, hot differentiation rate, ash
amount, and amount of fixed carbon. When using raw coals having the same
composition and properties, it is difficult to satisfy all these conditions.
Furthermore, with the use of the costly bitumen as a binder, unit
20 costs associated with the coal briquettes are increased, ultimately increasing
the cost to manufacture molten iron. Also, adjusting the amount of ash is
difficult such that SiO gas is generated in the hot combustion region formed
in a lower area of the coal-packed bed in the melter-gasifier by the SiO2
component comprised in the coals. The SiO gas is mixed into the molten
25 iron, which is melted while being reduced in the gasification region in the
coal-packed bed, to thereby increase the amount of Si contained in the
molten iron to thereby reduce the quality of the molten iron.
SUMMARY OF THE INVENTION
The method for manufacturing coal briquettes of the present
30 invention has been made to solve the above problems, and it relates to

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manufacture coal briquettes of a good quality by adding coals for controlling
quality to fine coals.
In addition, the present invention relates to provide method for
manufacturing molten irons using the method for manufacturing coal
5 briquettes.
Further, the present invention provides a more economical apparatus
for manufacturing molten irons that may be applied to actual equipment and
can use the method for manufacturing molten irons.
To achieve the above objects, the method for manufacturing coal
10 briquettes of the present invention used in manufacturing molten irons
includes a step of performing an initial grain size selection of a first coal
group to prepare fine coals; a step of mixing a second coal group having a
mean reflectance (Rm) of 0.8 or higher into the fine coals; a step of drying
mixed coals comprising the fine coals of the first coal group and the second
15 coal group, and performing a secondary grain size selection to the mixed
coals; a step of adding a hardening agent to the mixed coals and mixing the
hardening agent and the mixed coals; a step of adding a molasses binder to
the mixed coals and mixing the molasses binder and the mixed coals; and a
step of manufacturing coal briquettes by molding the mixed coals.
20 In the step of mixing a second coal group into the fine coals, the
second coal group may be mixed to 15-80wt% of the mixed coals.
In the step of adding a hardening agent, it is preferable that one or
more hardening agents are selected from the group consisting of quicklime,
slaked lime, limestone, calcium carbonate, cement, bentonite, clay, silica,
25 silicate, dolomite, phosphoric acid, sulfuric acid, and an oxide.
It is more preferable that the hardening agent is slaked lime.
In the step of adding a hardening agent, the hardening agent may be
quicklime and the quicklime may be converted to a slake lime according to
the chemical formula below.
30 CaO + H2O → Ca(OH)2

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In the step of adding a hardening agent, the hardening agent may be
quicklime, and the quicklime and the molasses binder may form calcium
saccharate bond.
In the step of adding a hardening agent, the hardening agent may be
5 added by an amount of 1-5 parts by weight of 100 parts by weight of the
mixed coals that have been dried and undergone grain size selection; and in
the step of adding the molasses binder, the molasses binder may be added
by an amount of 5-15 parts by weight.
In the step of drying the mixed coals and performing a secondary
10 grain size selection to the mixed coals, the water contents of the mixed coals
are preferably controlled to be 4-10wt% of the mixed coals.
In the step of manufacturing coal briquettes, the coal briquettes
preferably have 20-40% volatile matter contents, 20% or less coal ash
contents and 45-70% fixed carbon contents on a dry basis.
15 In the step of manufacturing coal briquettes, the coal briquettes
preferably contain 50% or less SiO2.
In the step of manufacturing coal briquettes, the coal briquettes may
have 80% or more coal briquettes of 10mm or greater in a cold strength
evaluation method. The cold strength evaluation method is performed by
20 allowing 2kg of a sample ore to undergo a free fall from a height of 5m onto a
steel plate four times and measuring the grain size of the remaining coal
briquettes.
In the step of manufacturing coal briquettes, the coal briquettes may
have 60% or more char with a grain size of 15mm or greater in a hot strength
25 evaluation method. The hot strength evaluation method is performed by
passing nitrogen gas in a reactor furnace set at 1000°C to obtain char in an
inert atmosphere, and measuring the grain size of the char.
To achieve the above objects, manufacturing molten irons of the
present invention relates to method for manufacturing molten irons in which
30 a coal-packed bed is formed by using coals and reduced irons that have

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undergone preliminary reduction is charged into the coal-packed bed. The
method for manufacturing molten irons include a step of performing an initial
grain size selection of a first coal group to prepare fine coals; a step of
mixing a second coal group having a mean reflectance (Rm) of 0.8 or higher
5 into the fine coals; a step of drying mixed coals comprising the fine coals of
the first coal group and the second coal group, and performing a secondary
grain size selection to the mixed coals; a step of adding a hardening agent to
the mixed coals and mixing the hardening agent and the mixed coals; a step
of adding a molasses binder to the mixed coals and mixing the molasses
10 binder and the mixed coals; a step of manufacturing coal briquettes by
molding the mixed coals; a step of forming a coal-packed bed using lump
coals that have been separated during the initial grain size selection and the
coal briquettes, and charging reduced irons for mixing into the coal-packed
bed; and a step of supplying oxygen to the coal-packed bed to burn coals in
15 the coal-packed bed, and manufacturing molten irons by melting reduced
irons using the heat of combustion.
In the step of mixing a second coal group into the fine coals, the
second coal group is preferably mixed to 15-80wt% of the mixed coals.
The step of drying the mixed coals and performing a secondary grain
20 size selection to the mixed coals may include a step of drying the mixed
coals, and a step of crushing the mixed coals with a grain diameter
exceeding 4mm among the dried mixed coals such that a grain diameter of
the mixed coals become 4mm or less are selected.
In the step of adding a hardening agent, one or more hardening
25 agents are selected from the group consisting of quicklime, slaked lime,
limestone, calcium carbonate, cement, bentonite, clay, silica, silicate,
dolomite, phosphoric acid, sulfuric acid, and an oxide.
In the step of adding a hardening agent, the hardening agent may be
added by an amount of 1-5 parts by weight of 100 parts by weight of the
30 mixed coals that have been dried and undergone grain size selection. Also,

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in the step of adding the molasses binder, the molasses binder may be
added by an amount of 5-15 parts by weight.
In the step of adding molasses binder, the molasses binder with a
solid content of 70-85wt% may be added.
5 In the step of manufacturing coal briquettes, the coal briquettes
preferably have 20-40% volatile matter contents, 20% or less coal ash
contents and 45-70% fixed carbon contents on a dry basis.
In the step of manufacturing coal briquettes, the coal briquettes
preferably contain 50% or less SiO2.
10 In the step of manufacturing coal briquettes, the volume of the coal
briquette is preferably 10-50cm3.
In the step of manufacturing coal briquettes, the coal briquettes
preferably have 80% or more coal briquettes of 10mm or greater in cold
strength evaluation method. The cold strength evaluation method is
15 performed by allowing 2kg of a sample ore to undergo a free fall from a
height of 5m onto a steel plate four times and measuring the grain size of the
remaining coal briquettes.
In the step of manufacturing coal briquettes, the coal briquettes
preferably have 60% or more char with a grain size of 15mm or greater in a
20 hot strength evaluation method. The hot strength evaluation method is
performed by passing nitrogen gas in a reactor furnace set at 1000°C to
obtain char in an inert atmosphere, and measuring the grain size of the char.
In the step of forming the coai-packed bed, the coal briquettes are
preferably in the range of 20-80wt% of coals used to form the coal-packed
25 bed.
In the step of manufacturing molten irons, the amount of dissolved Si
content in the molten irons is preferably 1wt% or less.
A step of recycling fine coals generated during manufacturing the
coal briquettes, and mixing the fine coals and the mixed coals can be further
30 included.

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In the step of manufacturing molten irons, reduced irons
manufactured by performing preliminary reduction of lump iron ores and
additives may be charged. Otherwise, iron ores of a small size and
additives may be preliminary reduced and hot compacted, and then reduced
5 irons may be charged.
The present invention relates to an apparatus for manufacturing
molten irons in which coals and reduced irons that have undergone
preliminary reduction are charged into a melter-gasifier to manufacture
molten irons. The apparatus for manufacturing molten irons includes a
10 grain size selector for performing an initial grain size selection of a first coal
group; a coal storage bin for supplying a second coal group having a mean
reflectance of 0.8 or greater, the coal storage bin performing this operation
separately from the grain size selector; a pretreating unit connected to the
grain size selector and the coal storage bin, and drying and performing a
15 secondary selection while mixing the fine coals of the first coal group and the
second coal group; at least one mixer connected to the pretreating unit, and
taking a molasses binder and a hardening agent for mixing with the mixed
coals in which the fine coals of a first coal group and the second coal group
are mixed; a roll press connected to the mixer for molding the mixed coals;
20 and a melter-gasifier connected to the grain size selector and the roll press,
and charged with lump coals separated from the grain size selector, the coal
briquettes molded in the roll press, and the reduced irons, and manufacturing
molten irons while being supplied with oxygen.
The apparatus for manufacturing molten irons may also include a
25 binder bin for supplying molasses binder; and a hardening agent bin for
supplying one or more hardening agents selected from the group consisting
of quicklime, slaked lime, limestone, calcium carbonate, cement, bentonite,
clay, silica, silicate, dolomite, phosphoric acid, sulfuric acid, and an oxide.
The binder bin and the hardening agent bin are preferably connected to the
30 mixer.

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The pretreating unit may comprise a drier connected to the grain size
selector and the coal storage bin, and drying the mixed coals in which the
fine coals of a first coal group and the second coal group are mixed; another
grain size selector for selecting coals having a grain diameter of 4mm or less
5 from the drier, and transporting the coals to the mixer; and a crusher for
crushing coals having a grain diameter that exceeds 4mm that have
undergone grain size selection.
The mixer preferably includes a kneader for kneading the mixed
coals and the molasses binder.
10 The apparatus for manufacturing molten irons of the present
invention may also include a recycling assembly connected to the roll press
and the mixer, and collecting fine coals generated during manufacturing coal
briquettes, and supplying the fine coals to the mixer.
The apparatus for manufacturing molten irons of the present
15 invention may also include coal briquette storage bin connected to the roll
press, for temporarily storing the coal briquettes molded in the roll press.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of an apparatus for manufacturing molten
irons according to a first embodiment of the present invention.
20 FIG. 2 is a schematic view of an apparatus for manufacturing molten
irons according to a second embodiment of the present invention.
FIG. 3 is a schematic view of a testing apparatus used for measuring
hot strength in experimental examples of the present invention.
FIG. 4 is a schematic view showing performance of a melter-gasifier
25 during manufacture of molten irons.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will now be described in detail
with reference to the accompanying drawings. The embodiments illustrate
the present invention and are not meant to be restrictive.
10

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The present invention provides a method of manufacturing molten
irons using coals with a wide distribution of a grain size. In order to ensure
permeability and prevent scattering in the melter-gasifier, the present
invention provides an apparatus for manufacturing molten irons that control
5 grain size of coals supplied to a meiter-gasifier to at least a predetermined
size. That is, in the apparatus and method for manufacturing molten irons
of the present invention, lump coals that exceed a predetermined size are
directly charged into the meiter-gasifier and coal briquettes manufactured by
compacting fine coals with equal or less than predetermined size are
10 charged into the meiter-gasifier to form a coal-packed bed. In addition, in
the apparatus and method for manufacturing molten irons of the present
invention, during manufacturing coal briquettes, coals for controlling quality
are mixed with fine coals and then mixed coals are molded into coal
briquettes to thereby ensure a predetermined hot strength and cold strength.
15 Accordingly, performance of the meiter-gasifier is improved and molten irons
of a good quality are produced.
If coals for controlling quality are mixed with fine coals in this manner,
the quality of molten irons may be improved by controlling various variables.
In particular, molten irons having a good quality can be manufactured by
20 controlling a reflectance of the coal for controlling quality, a mixing ratio of
the coals for controlling quality and fine coals, and a ratio of lump coals and
coal briquettes.
Especially, coal briquettes supplied through a coal supply assembly
included in an apparatus for manufacturing molten irons must satisfy the
25 following conditions during mixing the coals for controlling quality so that
molten irons having the desired properties may be manufactured.
(1) Grain size of coal must be limited to within a suitable range.
By satisfying this condition, hot combustion gas generated in a
combustion region is uniformly distributed in a coal-packed bed in a melter-
30 gasifier such that heat efficiency between the hot combustion gas and
n

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reduced irons and coals may be increased. Further, since a permeability of
the coal-packed bed may be suitably maintained, molten pig irons and slags
may uniformly flow downward within the coal-packed bed.
(2) Suitable level of cold strength of coal briquettes must be ensured.
5 By satisfying this condition, loss caused by the generation of powder
during the process of transporting and storing coal briquettes supplied to a
melter-gasifier may be minimized.
(3) Suitable level of hot differentiation rate must be ensured.
In the case where coal briquettes are charged into a melter-gasifier,
10 fine particles are generated by the hot differentiation rate resulting from quick
heating in a dome of the melter-gasifier. These fine particles ensure a
predetermined hot differentiation rate to thereby minimize the amount of
scattering loss to outside the melter-gasifier caused by a hot gas flow formed
in the dome.
15 (4) Suitable ievel of hot strength of coal briquettes must be ensured.
By satisfying this condition, a load of charged materials applied to an
upper area of a coal-packed bed and pressure of combustion gas from a
lower area in a region where gasification of a coal-packed bed in the melter-
gasifier occurs may be endured.
20 (5) There must be included suitable amount or less of coal ashes in
raw coals.
By satisfying this condition, an amount of slags produced by a slag
reaction between coals in a region where gasification occurs and gangue
components in reduced irons are maintained at a predetermined level or less.
25 (6) Suitable level of fixed carbons must be ensured.
By satisfying this condition, it is possible to prevent the shortage
amount of carbons that are heated and supplied from a region where
gasification occurs to a region where combustion occurs.
In the present invention, condition (1) is satisfied through a grain size
30 selection process, condition (2) is satisfied by mixing a suitable binder with
12

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coals, and conditions (3) through (6) are satisfied by suitably using a coal for
controlling quality. If coals for controlling quality are not separately used for
mixing, and lump coals and coal briquettes as coals are only supplied to a
melter-gasifier, it is difficult to satisfy conditions (3) through (6).
5 An apparatus and method for manufacturing molten iron of the
present invention for satisfying the above conditions with respect to the
properties of coal briquettes will be described below in greater detail.
FIGs. 1 and 2 is schematic views of apparatus for manufacturing
molten iron respectively according to first and second embodiments of the
10 present invention. FIG. 1 shows an apparatus for manufacturing molten
irons 10 using a packed bed-type reactor 100, and FIG. 2 shows an
apparatus for manufacturing molten irons 20 using a fluidized bed-type
reactor 200. Each of the apparatus 10 and 20 includes a coal supply
assembly 400 having the same structure, and coals are supplied to a melter-
15 gasifier 300 through the coal supply assembly 400 to form a coal-packed bed.
In the apparatus for manufacturing molten irons 10 according to a
first embodiment of the present invention as shown in FIG. 1, lump iron ores
and additives are mixed and undergone preliminary reduction in the packed
bed-type reactor 100 to manufacture reduced irons. Next, reduced irons
20 are charged into the coal packed bed in the melter-gasifier 300, thereby
manufacturing molten irons. The coal packed bed is made of the coals
supplied from the coal supply assembly 400.
In the apparatus for manufacturing molten iron 20 according to a
second embodiment of the present invention as shown in FIG. 2, iron ores
25 with a small grain size and additives are mixed to undergo preliminary
reduction in the fluidized bed-type reactor 200. Next, hot compacted
reduced irons are supplied from a hot compacting assembly 220 connected
to the fluidized bed-type reactor 200 to a coal-packed bed, which is formed
with coals supplied from the coai supply assembly 400. Then, molten irons
30 are manufactured in the melter-gasifier 300. The hot compacted materials
13

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are supplied to the melter-gasifier 300 through a hot intermediate vessel
assembly 240 such that it is possible to maintain supply amount suitably.
The coal supply assembly 400 common to both the apparatuses for
manufacturing molten irons 10 and 20 according to the first and second
5 embodiments of the present invention, respectively will be described below.
The apparatuses for manufacturing molten irons according to the first
and second embodiments of the present invention includes a grain size
selector 411 for performing an initial grain size selection of a first coal group;
a coal storage bin 417 for supplying a second coal group having a mean
10 reflectance of 0.8 or greater as coals for controlling quality, the coal storage
bin 417 performing this operation separately from the grain size selector 411;
a pretreating unit 419 connected to the grain size selector 411 and the coal
storage bin 417, and drying and performing a secondary selection while
mixing the fine coals of the first coal group and the second coal group; at
15 least one mixer 425 connected to the pretreating unit 419 and taking a
molasses binder and a hardening agent for mixing with the mixed coals in
which the fine coals of a first coal group and the second coal group are
mixed; a roll press 427 connected to the mixer 425 for molding the mixed
coals; and a melter-gasifier 300 connected to the grain size selector 411 and
20 the roll press 427. The lump coals separated from the grain size selector
411, the coal briquettes molded in the roll press 427, and the reduced irons
are charged into the melter-gasifier 300. Then, molten irons are
manufactured in the melter-gasifier 300 while being supplied with oxygen.
The above apparatuses are included in the coal supply assembly 400.
25 Molten irons and slags are manufactured in the melter-gasifier 300. The
first coal group and the second coal group are not mixed using another
process, but are freely mixed through the process in order. For example,
the second coal group can be dumped on a conveyor belt while transporting
the first coal group using a conveyor belt, thereby both the first coal group
30 and the second coal group can be mixed together.
14

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Further, the apparatuses for manufacturing molten irons according to
the first and second embodiments of the present invention comprise a binder
bin 423 for supplying molasses binder for binding coals; and a hardening
agent bin 421 for supplying one or more hardening agents selected from the
5 group consisting of quicklime, slaked lime, limestone, calcium carbonate,
cement, bentonite, clay, silica, silicate, dolomite, phosphoric acid, sulfuric
acid, and an oxide. The hardening agent bin 421 is separated from the
binder bin 423. The binder bin 423 and the hardening agent bin 421 are
connected to the mixer 425.
10 The mixer 425 may include an additional mixer for separately mixing
the molasses binder and the hardening agent, and may include a kneader for
kneading them together.
The pretreating unit 419, as shown in the enlarged rectangle of FIG.
1, includes a drier 459 connected to the grain size selector 411 and the coal
15 storage bin 417, and drying the mixed coals in which the fine coals of a first
coal group and the second coal group are mixed; another grain size selector
461 for selecting coals having a grain diameter of 4mm or less from the drier
459; and a crusher 463 for crushing coals having a grain diameter that
exceeds 4mm that have undergone grain size selection. The pretreating
20 unit 419 may further include a mixed coal storage bin 465 for selectively and
temporarily storing coals with a grain diameter of 4mm or less. This may be
applied to not only the first embodiment of the present invention, but also to
the second embodiment of the present invention as shown in FIG. 2.
Among the raw coals, lump coals with a grain diameter that exceeds
25 8mm incapable of passing through the grain size selector 411 passes
through a lump coal drying assembly 413 to be dried, then is charged directly
into the melter-gasifier 300. Lump coals are dried in the lump coal drying
assembly 413, thereby controlling moisture contents in the lump coais to be
4wt% or less. On the other hand, fine coals of a first coal group that pass
30 through the grain size selector 411 are stored in a fine coal storage bin 415,
15

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then are mixed with the second coal group for controlling quality stored in
coal storage bin 417 and molded to be coal briquettes. The coal briquettes
are then temporarily stored in a coal briquette bin 431 and are supplied to
the melter-gasifier 300.
5 The apparatuses according to the first and second embodiments of
the present invention further include a recycling assembly 440 that is
connected to the roll press 427, and that collects fine coals generated during
manufacturing coal briquettes and supplies the same to the mixer 425. The
recycling assembly 440 includes a fine coal selector 429, a fine coal storage
10 bin 433, and a recycling pipe 435. In addition, the recycling assembly 440
may include additional devices required to perform recycling. The recycling
assembly 440 supplies fine coals selected in the fine coal selector 429 to the
fine coal storage bin 433 for temporarily storing in the same through the
recycling pipe 435, then supplies the fine coals to the mixer 425 therethrough.
15 Molten irons are manufactured through each of the following step
using the apparatuses for manufacturing molten irons according to the first
and second embodiments of the present invention.
The method for manufacturing coal briquettes includes a step of
performing an initial grain size selection of a first coal group as raw coals to
20 prepare fine coals; a step of mixing a second coal group having a mean
reflectance (Rm) of 0.8 or higher into the fine coals; a step of drying mixed
coals comprising the fine coals of the first coal group and the second coal
group, and a step of performing a secondary grain size selection to the
mixed coals; a step of adding a hardening agent to the mixed coals and
25 mixing the hardening agent and the mixed coals; a step of adding a
molasses binder to the mixed coals and mixing the molasses binder and the
mixed coals; and a step of manufacturing coal briquettes by molding the
mixed coals.
The method for manufacturing molten irons includes a step of
30 forming a coal-packed bed using lump coals that have been separated
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during the initial grain size selection and the coal briquettes, and charging
reduced irons for mixing into the coal-packed bed; and a step of supplying
oxygen to the coal-packed bed to burn coals in the coal-packed bed, and a
step of manufacturing molten irons by melting reduced irons using the heat
5 of combustion. The step of adding a molasses binder to the mixed coals
may comprise a kneading process to mix them more uniformly.
The coal group refers to an aggregate of coal in which at least one or
more types of coal are mixed. The 8mm grain diameter standard of the
initial grain size selection is used to distinguish between lump coals and fine
10 coals. Since it is preferable that lump coals with a grain diameter exceeding
8mm should be used and separated from the fine coals of 8mm or less in the
packed bed-type reactor for manufacturing molten irons, the above standard
is applied to perform grain size selection. The above standard is merely an
example of the present invention and the present invention is not limited
15 thereto. Therefore, it is possible to perform grain size selection using
another standard.
Further, coals with a mean reflectance (Rm) of 0.8 or higher are
mixed with fine coals. In analyzing coal structure, in case of calculating a
content ratio of constituent structural components and minute structural
20 components using a microscope, the reflectance is indicated by the
amplitude or energy of the reflected light, and the amplitude or energy of the
incident light when light is directed onto the surface of a material object.
The mean reflectance of the coal that is used is determined by measuring a
maximum reflectance of the minute structural components using a
25 microscope and light with a wavelength of 546nm. Coal may be evaluated
by the reflectance of vitrinite, which is a main component of coal, and the
mean reflectance is proportional to hot strength. Therefore, the higher the
mean reflectance, the greater the hot strength of coal briquettes such that
performance of the coal briquettes in the melter-gasifier is made more
30 favorable.
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In the case where the mean reflectance (Rm) of coal for controlling
quality is less than 0.8, the coal for controlling quality is quickly turned to
differentiate such that not only its hot strength is low, but it is unable to
sufficiently operate as a heat source. Accordingly, it is preferable that the
5 mean reflectance of the coal for controlling quality should be 0.8 or greater.
Coking coal is an example of coal for controlling quality. In the case of coal,
the mean reflectance typically does not surpass 3.0.
When mixing a second coal group as coals for controlling quality into
fine coals in the present invention, it is preferable that the second coal group
10 should be added until their amounts are 15-80wt% of the mixed coals. If
the coals for controlling quality are less than 15wt% of the mixed coals, it
becomes difficult to improve the characteristics of the fine raw coals.
Further, if the coals for controlling quality exceed 80wt% of the mixed coals,
there is only a minimal increase in the properties of the coal briquettes in
15 high temperature relative to the increase in the raw material costs of the coal
briquettes.
In the present invention, molasses binder and a hardening agent
may be added and mixed. Preferably, with respect to mixed coals of 100
parts by weight that have been dried and have undergone grain size
20 selection, the hardening agent is 1-5 parts by weight and the molasses
binder is 5-15 parts by weight.
If quicklime (CaO), which is one of hardening agent, is mixed with
the mixed coals, residual water in the mixed coals reacts with the quicklime
(CaO) to be converted into calcium hydroxide [Ca(OH)2] through the
25 chemical reaction shown by Chemical Formula 1 below to thereby removing
water by a strong calorification reaction. A subsequent molding process is
favorably realized by removing water content, and a predetermined strength
is ensured.
[Chemical Formula 1]
30 CaO + H2O →Ca(OH)2
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If water is removed in this manner and molasses binder is used as a
binder, the quicklime and molasses binder improve the strength of coal
briquettes by the chemical reaction of calcium saccharate bond, and melting
of the molasses binder in the water is prevented.
5 In the present invention, it is preferable that a hardening agent be
added by an amount of 1-5 parts by weight with respect to 100 parts by
weight of the mixed coals. If the amount of hardening agent is less than 1
part by weight, water may not be sufficiently removed such that good calcium
saccharate bond between the molasses binder and the hardening agent is
10 unable to be realized, resulting in a reduction in the strength of the coal
briquettes. In addition, if the hardening agent exceeds 5 parts by weight,
the properties of the coal briquettes deteriorate.
It is preferable that molasses binder be added by an amount of 5-15
parts by weight. If the amount of added molasses binder is less than 5
15 parts by weight, the strength of the coal briquettes is reduced due to the
insufficient amount of molasses binder in the fine coals. Also, if the amount
of added molasses binder is greater than 15 parts by weight, adhesion and
other such problems occur during mixing with fine coals. In the case of
molasses binder, it is preferable that the amount of solid content is 70-85wt%.
20 If the amount of solid content is less than 70wt%, the content of sugar, which
exhibits binding property, is low and the water content is high such that the
strength of the coal briquettes is reduced. Also, if the amount of solid
content exceeds 85wt%, the viscosity of the binder is increased such that it
is difficult to realize uniform mixing.
25 In the above, although a molasses binder is added, the present
invention is not limited in this respect and it possible to realize mixing other
binders and other additives that improve the properties of other binders and
coal briquettes.
Further, in the present invention, a step of drying the mixed coals
30 and performing secondary grain size selection may comprise a step of drying
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the mixed coals, and a step of crushing mixed coals with a grain diameter
that exceeds 4mm in the dried mixed coals such that the grain diameter of
the mixed coals becomes 4mm or less. It is preferable that the amount of
water in the mixed coals become 4-10 wt% of the total in consideration of the
5 mixing amount with the hardening agent. If the amount of water in the
mixed coals is less than 4%, there is an insufficient reaction between the
mixed coals and hardening agent such that the strength of ultimately
manufactured coal briquettes is reduced. Further, if the amount of water in
the mixed coals exceeds 10wt%, adhesion and cohesion occur in the
10 molding process such that yield and operating efficiency are reduced. In
addition, if the grain diameter of the mixed coals exceeds 4mm, the coal
briquettes may be broken during molding the same as a result of the large
grain diameter. The grain diameterof the coals, therefore, must be
controlled to 4mm or less.
15 The coal briquettes molded by the roll press 427 preferably has 20-
40% volatile matter contents, 20% or less coal ash contents, and 45-70%
fixed carbon contents on a dry basis. If the amount of volatile matters are
less than 20%, the amount of generated gas needed in the reduction of iron
ores is minimized such that reduction is not sufficiently realized and fuel
20 costs are increased. If the amount of volatile matters exceeds 40%, the
amount of fixed carbons needed in manufacturing molten irons is reduced.
Further, if the amount of coal ashes content exceeds 20%, fuel costs
increase as a result of the increase in the slag volume. Also, fuel costs
increase if the amount of fixed carbon is less than 45%, while if the amount
25 of fixed carbon exceeds 70%, the amount of gas needed for reduction of ore
is decreased such that reduction is not sufficiently realized and fuel costs are
increased.
Regarding the composition of coal ashes comprised in coal
briquettes, it is preferable that the content of SiO2 should be 50% or less. If
30 the SiO2 content in the coal ash exceeds 50%, the amount of Si in the molten
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irons is increased such that the quality of the molten irons is decreased.
Further, it is necessary that the coal briquettes have a sufficient cold
strength for transporting and storing, and must have a sufficient hot strength
to minimize the generation of fine particles so that permeation rate may be
5 ensured during charging to the melter-gasifier.
With respect to a method for evaluating the cold strength of coal
briquettes, 2kg of a sample ore is allowed to undergo a free fall from a height
of 5m onto a steel plate. This is performed four times. Next, the amount of
remaining coal briquettes with a grain diameter of 10mm or more is
10 determined. It is preferable that the amount of coal briquettes remaining
with a 10mm or greater grain diameter is 80% or more. If the amount is less
than 80%, an increase in a differentiation rate during transporting and storing
coal briquettes causes operating expenses to increase, and makes
production unstable as a result of the negative affect on production
15 processes. Also, yield is decreased by the reduction in the temperature of
the molten irons in the melter-gasifier.
With respect to a method for evaluating the hot strength of coal
briquettes, nitrogen gas is passed through a reaction furnace set at 1000 °C,
and a grain size of the obtained char in an inert atmosphere is divided into a
20 ratio of a relatively large grain size of 15mm or greater and a ratio of a
relatively small grain size of 10mm or less. The greater the large grain size
ratio and the less the small grain size ratio, the greater the hot strength of the
coal briquettes. It is preferable that the large grain size ratio is 60% or more
of the total to ensure a good hot strength of the coal briquettes. If the large
25 grain size ratio of the char in the hot strength evaluation method of coal
briquettes is less than 60%, the coal briquettes are insufficiently burned in
the melter-gasifier, and are excessively collected in a dust collector to
thereby increase manufacturing costs and fuel costs.
There is a difference in the volume of coal briquettes and lump coals
30 when charged into the melter-gasifier. Coal briquettes are manufactured
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having a uniform volume of 10-50cm3, preferably 20-40cm3. Since the sizes
of lump coals obtained in a natural state are smaller than those of coal
briquettes, larger coal briquettes is preferred to use in consideration of
ventilation. The above range of volume for coal briquettes is an optimal
5 value in order to ensure good ventilation in consideration of the volume of
lump coals.
If coal briquettes manufactured in this manner and lump coals with a
grain diameter that exceeds 8mm are charged together into the melter-
gasifier to form a coal-packed bed, lump coals with their natural components
10 and properties may not be suitable for the component and property
standards of the melter-gasifier. Therefore, it is preferable that the amount
of coal briquettes used be adjusted according to the components and
properties of the lump coals to meet the component and property standards
of the melter-gasifier. Accordingly, coal briquettes in an amount of 20-
15 80wt% of the total coal are used for charging to the melter-gasifier. If the
amount of coal briquettes is less than 20wt% of the total coals, it is difficult to
make improvements in the gas distribution, gasification, combustion reaction,
flow of molten irons and slags, and so on. If the amount of the coal
briquettes exceeds 80wt%, the amount of lump coals that is used is
20 excessively minimized such that problems occur with respect to effectively
managing stocks of raw coals.
Especially, if molten irons are manufactured using only lump coals,
the amount of SiO2 charged is approximately 100kg per ton of coal such that
SiO2 is generated in the hot combustion region formed in a lower area of the
25 coal-packed bed to be mixed in the molten irons that is reduced and melted
in the gasification region in the coal-packed bed, thereby increasing the [Si]
content in the molten iron. On the contrary, since the amount of coal ashes
in the raw material coal may be reduced and controlled when charging coal
briquettes, in which coal for controlling quality has been mixed, the charging
30 amount of SiO2 is reduced to approximately 55kg per 1 ton of coal briquettes
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to thereby minimize the amount of SiO gas generated. Ultimately, the [Si]
content in the molten iron is reduced.
If molten irons are manufactured using the coal briquettes
manufactured through the above method, it is preferable that the dissolved
5 Si content in the molten irons is 1wt% or less. If the dissolved Si content in
the molten irons is greater than 1wt%, the quality of the molten irons is
reduced.
In the following, the present invention is described in greater detail
through Experimental Examples. The following Experimental Examples
10 merely illustrate the present invention are not meant to be restrictive.
Experimental Examples
In the Experimental Examples that follow, the following experiments
were performed in an attempt to manufacture molten irons of a good quality
by adjusting the reflectance and mixing ratio of the coals for controlling
15 quality, and the amount of coal briquettes used. Experimental Examples of
the present invention are described in which the reflectance and mixing ratio
of the coals for controlling quality, and the amount of coal briquettes used
are varied.
Reflectance and mixing ratio of coals for controlling quality
20 In the Experimental Examples of the present invention, various types
of coals having different mean reflectance (Rm) were mixed to manufacture
coal briquettes, then their hot strength were measured. This is shown in
Table 1 below. In order to increase the quality of fine coals, coal groups for
controlling quality having a mean reflectance that is higher than that of fine
25 coals were used for mixing with the same.
Table 1]

Coal Group Technical Analysis (on dry basis, wt%) mean
reflectance
(Rm)

Volatile
matter Coal ash Fixed carbon

A 16.6 8.5 74.9 1.45
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B 18.0 14.1 67.9 1.27
C 19.1 6.9 74.0 1.00
D 34.8 6.8 58.3 0.80
E 34.4 7.4 58.2 0.71
F 26.2 10.4 63.4 0.78
G 34.0 9.4 56.6 0.68
In Experimental Examples 1 through 8 of the present invention, after
mixing of the A-type coal group through F-type coal group having a grain
diameter of 4mm or less, 8 parts by weight of molasses binder as a binder
5 and 3 parts by weight of quicklime as a hardening agent based on 100 parts
by weight of the mixed coals were mixed to manufacture coal briquettes of a
pillow shape and having the dimensions of 64.5mm x 25.4mm x 19.1mm
using a roll press. The hot strength of the coal briquettes was then
measured. Further, for comparison with Experimental Examples 1 through
10 10, in Comparative Examples 1 through 3, 8 parts by weight of molasses
binder as a binder and 3 parts by weight of quicklime as a hardening agent
were mixed in one of the E-type coal group and the F-type coal group, which
have properties similar to that of fine coals, and coal briquettes were
manufactured using a roll press. The hot strength of the coal briquettes
15 was then measured. In the case of the G-type coal group, lump coals were
used in place of coal briquettes and their hot strength was measured.
The measurement of hot strength to determine the amount of
pyrolysis of the coal briquettes generated in the melter-gasifier was
performed using a pyrolysis testing apparatus 30 of FIG. 3. FIG. 3 is a
20 schematic view of a pyrolysis testing apparatus used for measuring a hot
strength of coal briquettes of the Experimental Examples of the present
invention. The temperature of the pyrolysis testing apparatus 30 was
maintained at 1000°C, and nitrogen gas was passed through a lower portion
thereof at a rate of 2 liters per minute to maintain an inert atmosphere.
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Under these conditions, coal briquettes test pieces 36 were supplied into a
quartz pipe 33, having a diameter of 60mm, two at a time at 10 minutes
intervals. This was repeated four times to test a total of 8 coal briquette test
pieces 36. After supplying the coal briquette test pieces 36, a sample ores
5 were extracted and cooled, and variations in grain size distributions were
measured using a standard sieve. Since the lower the degree of pyrolysis,
the higher the hot strength, the hot strength is determined to be good if there
is a significant amount of large char and a minimal amount of small char. In
the Experimental Examples of the present invention, the hot strength was
10 determined by examining the distribution of char with a large grain size of
15mm or greater and char with a small grain size of 10mm or less.
Experimental Example 1
With reference to Table 1, after mixing the E-type coal group at
70wt% and the A-type coal group at 30wt%, 8 parts by weight of molasses
15 binder as a binder and 3 parts by weight of quicklime as a hardening agent
were mixed to manufacture coal briquettes. The hot strength of the coal
briquettes was then measured.
Experimental Example 2
With reference to Table 1, except for mixing the E-type coal group at
20 70wt% and the B-type coal group at 30wt%, all other aspects of
Experimental Example 2 were identical to Experimental Example 1.
Experimental Example 3
With reference to Table 1, except for mixing the E-type coal group at
70wt% and the C-type coal group at 30wt%, all other aspects of
25 Experimental Example 3 were identical to Experimental Example 1.
Experimental Example 4
With reference to Table 1, except for mixing the E-type coal group at
50wt% and the C-type coal group at 50wt%, all other aspects of
Experimental Example 4 were identical to Experimental Example 1.
30 Experimental Example 5
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With reference to Table 1, except for mixing the F-type coal group at
20wt% and the B-type coal group at 80wt%, all other aspects of
Experimental Example 5 were identical to Experimental Example 1.
Experimental Example 6
5 With reference to Table 1, except for mixing the E-type coal group at
80wt% and the D-type coal group at 20wt%, all other aspects of
Experimental Example 6 were identical to Experimental Example 1.
Experimental Example 7
With reference to Table 1, except for mixing the E-type coal group at
10 85wt% and the D-type coal group at 15wt%, all other aspects of
Experimental Example 7 were identical to Experimental Example 1.
Experimental Example 8
With reference to Table 1, except for mixing the E-type coal group at
50wt% and the F-type coal group at 50wt%, all other aspects of
15 Experimental Example 8 were identical to Experimental Example 1.
Experimental Example 9
With reference to Table 1, except for mixing the E-type coal group at
10wt% and the A-type coal group at 90wt%, all other aspects of
Experimental Example 9 were identical to Experimental Example 1.
20 Experimental Example 10
With reference to Table 1, except for mixing the E-type coal group at
10wt% and the B-type coal group at 90wt%, all other aspects of
Experimental Example 10 were identical to Experimental Example 1.
Comparative Example 1
25 With reference to Table 1, except for using the E-type coal group at
100wt%, all other aspects of Comparative Example 1 were identical to
Experimental Example 1.
Comparative Example 2
With reference to Table 1, except for using the F-type coal group at
30 100wt%, all other aspects of Comparative Example 2 were identical to
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Experimental Example 1.
Comparative Example 3
Only lump coals were used for ail of the G-type coal group, and coal
briquettes were not used.
5 The hot strengths of the coal briquettes manufactured according to
the Experimental Examples and the Comparative Examples were measured
and appear in Table 2 below.
[Table 2]

Coal mixing ratio Hot strength
(Large grain
size ratio) Hot strength
(Small grain
size ratio)
Experimental
Example 1 E/70wt% A/30wt% 75.0% 2.2%
Experimental
Example 2 E/70wt% B/30wt% 72.2% 1.2%
Experimental
Example 3 E/70wt% C/30wt% 66.8% 1.2%
Experimental
Example 4 E/50wt% C/50wt% 65.9% 2.6%
Experimental
Example 5 F/20wt% B/80wt% 87.8% 1.5%
Experimental
Example 6 E/80wt% D/20wt% 65.1% 1.8%
Experimental
Example 7 E/85wt% D/15wt% 60.7% 2.9%
Experimental
Example 8 E/50wt% F/50wt% 54.5% 2.7%
Experimental
Example 9 E/10wt% A/90wt% 86.5% 1.9%
Experimental
Example 10 E/10wt% B/90wt% 90.9% 1.4%
Comparative
Example 1 E/100wt% - 56.5% 7.2%
Comparative
Example 2 F/100wt% - 50.1% 2.9%
Comparative
Example 3 G/100wt% - 57.0% 2.8%
10 When lump coals are only used without coal briquettes to
manufacture molten irons as in Comparative Example 3, the hot strength is
approximately 57.0%. Therefore, the hot strength when manufacturing coal
briquettes by mixing coals must be better than that when only using lump
coals, thereby ensuring more economical production.
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As shown in Table 2, in the case of Experimental Examples 1
through 7, and Experimental Examples 9 and 10, the ratio of char with a
grain diameter of 15mm or greater is at least 60%, and the ratio of char with
a grain diameter of 10mm or less does not exceed 3% such that hot strength
5 is relatively high. On the other hand, in the case of Experimental Example 8
and Comparative Examples 1 through 3, the ratio of char with a grain
diameter of at least 15mm is less than 60%, and the ratio of char with a grain
diameter of 10mm or less is at least 2.7%, indicative of a relatively low hot
strength.
10 In addition, as is evident from the Experimental Examples 5, 9, and
10, when there is mixed as coals for controlling quality respectively 80wt% of
the B-type coal group, 90wt% of the A-type coal group, and 90wt% of the B-
type coal group, there are only slight variations in the hot strength, with the
respective hot strength being 87.8%, 86.5%, and 90.9%.
15 It is evident from the above Experimental Examples that a relatively
high hot strength may be obtained if coal briquettes are manufactured by
mixing coals of which reflectance is equal to or more than that of the D-type
coal group. Accordingly, it is preferable that the mean reflectance of coals
for quality control should be at least that of the D-type coal group, 0.8. It is
20 more preferable that the mean reflectance of coals for quality control should
be the B-type coal group, 1.27 in order for the hot strength to be over
70.0wt%
Further, it is evident from Experimental Example 7 that the coals for
controlling quality must be added by an amount of at least 15% to obtain coal
25 briquettes having a favorable hot strength.
Usage Ratio of coal briquettes
In the Experimental Examples of the present invention, when
manufacturing coal briquettes of Experimental Examples 2 and 3, the
properties of the molten irons according to the amount of coal briquette used
30 were determined through the following experiments.
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15
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Using Coal briquettes of Experimental Example 2
In order to determine the properties of molten iron according to a
mixing ratio of coal briquettes and lump coals, the amount of coal briquettes
manufactured according to Experimental Example 2 that is used was
adjusted to perform the following experiments. Results of the experiments
appear in Table 3.
Experimental Example 2-1
After mixing the E-type coal group at 70wt% and the B-type coal
group at 30wt% as in Experimental Example 2, coal briquettes were
manufactured by mixing 8 parts by weight of molasses binder as a binder
and 3 parts by weight of quicklime as a hardening agent. Coal briquettes
were used in 20wt% of the charged coals, and lump coals were used in the
remaining 80wt% of the charged coals.
Experimental Example 2-2
Coal briquettes of Experimental Example 2 were used in 30wt% of
the charged coals, and lump coals were used in the remaining 70wt% of the
charged coals.
Experimental Example 2-3
Coal briquettes of Experimental Example 2 were used in 50wt% of
the charged coals, and lump coals were used in the remaining 50wt% of the
charged coals.
Comparative Example 4
Only lump coals were supplied to the melter-gasifier, and coal
briquettes were not used.

25

[Table 3]

Experimental
Example 2-1 Experimental
Example 2-2 Experimental
Example 2-3 Comparative
Example 4
Coal briquette usage
ratio (wt%) 20 30 50 0
Fuel cost (t/h) 1037 1031 1019 1055
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PCT/KR2005/000218
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Melter-
gasifier
pressure
difference
(kg/cm2) Wind
pressure 4.4 4.3 4.0 4.5

Pressure
loss 2.02 1.82 1.75 2.03
Molten iron
temperature (°C) 1503 1520 1520 1493
[Si] in molten iron (%) 0.72 0.60 0.50 1.13
As shown in Table 3, as the amount of coal briquettes used is
increased from 20wt%, the wind pressure and pressure loss in the meiter-
gasifer is stabilized such that gas distribution becomes uniform and
5 ventilation is improved. This is due to the fact that, as coal briquettes are
used, the grain size of the charged coals becomes uniform, and the char
particles become stable at high temperature. Accordingly, there is an
increase in the efficiency of heat exchange between gas rising from a lower
area of the melter-gasifier and reduced irons descending from an upper area
10 of the melter-gasifier. This results in an increase in the yield speed of
molten irons and a reduction in fuel costs.
Using Coal briquettes of Experimental Example 3
In order to determine the properties of molten irons according to the
mixing ratio of coal briquettes and lump coals, the amount of coal briquettes
15 manufactured according to Experimental Example 3 that is used was varied
and the following experiments were performed. Results of the experiments
appear in Table 4 below.
Experimental Example 3-1
After mixing the E-type coal group at 70wt% and the C-type coal
20 group at 30wt% as in Experimental Example 3, coal briquettes were
manufactured by mixing 8 parts by weight of molasses binder as a binder
and 3 parts by weight of quicklime as a hardening agent. Coal briquettes
are used as 20wt% of the charged coal amount, and lump coals are used as
the remaining 80wt% of the charged coal amount. A small amount of cokes
25 was then supplied to maintain stable operating conditions of the melter-
30

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gasifier.
Experimental Example 3-2
Coal briquettes of Experimental Example 3 were used in 40% of the
charged coal amount, and lump coals were used the remaining 60wt% of the
charged coai amount. A small amount of coke was then supplied to
maintain stable operating conditions of the melter-gasifier.
Experimental Example 3-3
Coal briquettes of Experimental Example 3 were used in 50% of the
charged coal amount, and lump coals were used in the remaining 50wt% of
the charged coal amount.
Comparative Example 5
Only lump coals were supplied to the melter-gasifier, and coal
briquettes were not used. A small amount of coke was then supplied to
maintain stable operating conditions of the meiter-gasifier.
[Table 4]

Experimental
Example 3-1 Experimental
Example 3-2 Experimental
Example 3-3 Comparative
Example 5
Coal briquettes usage ratio
(wt%) 20 40 50 0
Melter-
gasifier Cokes usage ratio 10 8 0 12

Molten
iron
temperat
ure(°C) Average 1498 1503 1507 1497

Deviation 6.9 5.7 4.4 12.9

[Si] in
molten
iron (%) Average 0.92 0.90 0.59 1.15

Deviation 0.12 0.11 0.10 0.15

20

As is evident from the results shown in Table 4, as the amount of
coal briquettes used is increased from 20wt%, the deviation in the
temperature of the molten irons gradually decreases. Further, when coal
briquettes were used in 50% of the charged coals as in Experimental
Example 3-3, the [Si] amount in the molten iron is significantly decreased to
0.59%, and as the amount of coal briquettes used is increased, the

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temperature of molten irons and concentration of [Si] in molten iron are
significantly reduced.
In addition, with increases in the amount of coai briquettes that were
used, the gas flow distribution is made to be uniform by the increase in
5 permeability of the coal-packed bed, and the strength of the coal briquette
char is increased to significantly improve a fluid permeability in a lower area
of the coal-packed bed. Therefore, the amount of cokes used is gradually
decreased such that when 50wt% of coal briquettes are used as in
Experimental Example 3-3, stable operation was able to be maintained even
10 without using cokes.
On the other hand, when coal briquettes were not used and only
lump coals were used as in Comparative Example 5, the gas flow distribution
in the coal-packed bed becomes uniform, and the fluid permeability therein is
improved. To control the gasification reaction, it was necessary to use less
15 reactive cokes of a high strength in an amount of approximately 12 parts by
weight.
In the present invention described above, coal briquettes using coals
with a large distribution of grain sizes are suitable for the manufacture of
molten irons, as long as coals for controlling quality with a mean reflectance
20 of 0.8 and higher are used.
In addition, by controlling to predetermined amounts the mean
reflectance of coals for controlling quality, the mixing ratio of molasses binder
and a hardening agent, the mixing ratio of fine coals and coals for controlling
quality, and the amount of coal briquettes used, various conditions such as
25 hot differentiation rate, hot strength, coal ash amount, and fixed carbon
amount in the melter-gasifer required for manufacturing molten irons may be
satisfied.
Furthermore, the apparatus for manufacturing molten irons of the
present invention uses a pretreating unit to repeat drying and grain size
30 selection such that the final quality of the coal briquettes is improved.
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The apparatus for manufacturing molten irons of the present
invention separately uses binder bin to enable the amount of molasses
binder supplied to be suitably controlled, thereby making process much
easier.
5 Also, in the apparatus for manufacturing molten irons of the present
invention, the mixer may include a kneader such that the mixed coals and
the molasses binder are bonded well, thereby improving the ultimate quality
of the coal briquettes.
The apparatus for manufacturing molten irons of the present
10 invention also includes a coal briquette storage bin for temporarily storing the
manufactured coal briquettes. As a result, the amount of coal briquettes
charged into the melter-gasifier may be flexibly controlled depending on the
production conditions.
Although embodiments of the present invention have been described
15 in detail hereinabove in connection with certain exemplary embodiments, it
should be understood that the invention is not limited to the disclosed
exemplary embodiments, but, on the contrary is intended to cover various
modifications and/or equivalent arrangements included within the spirit and
scope of the present invention, as defined in the appended claims.
20
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WHAT IS CLAIMED IS:
1. A method for manufacturing coal briquettes using in manufacturing
molten irons, the method comprising the steps of:
performing an initial grain size selection of a first coal group to
5 prepare fine coals;
mixing a second coal group having a mean reflectance (Rm) of 0.8
or higher into the fine coals;
drying mixed coals comprising the fine coals of the first coal group
and the second coal group, and performing a secondary grain size selection
10 to the mixed coals;
adding a hardening agent to the mixed coals and mixing the
hardening agent and the mixed coals;
adding a molasses binder to the mixed coals and mixing the
molasses binder and the mixed coals; and
15 manufacturing coal briquettes by molding the mixed coals.
2. The method of claim 1, wherein in the step of mixing a second
coal group into the fine coals, the second coal group is mixed to 15-80wt% of
the mixed coals.
20
3. The method of claim 1, wherein in the step of adding a hardening
agent, one or more hardening agents are selected from the group consisting
of quicklime, slaked lime, limestone, calcium carbonate, cement, bentonite,
clay, silica, silicate, dolomite, phosphoric acid, sulfuric acid, and an oxide.
25
4. The method of claim 3, wherein the hardening agent is slaked lime.
5. The method of claim 3, wherein in the step of adding a hardening
agent, the hardening agent is quicklime and the quicklime is converted to a
30 slake lime according to the chemical formula below.
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CaO + H2O → Ca(OH)2
6. The method of claim 3, wherein in the step of adding a hardening
agent, the hardening agent is quicklime, and the quicklime and the molasses
5 binder forms calcium saccharate bond.
7. The method of claim 1, wherein in the step of adding a hardening
agent, the hardening agent is added by an amount of 1-5 parts by weight of
100 parts by weight of the mixed coals that have been dried and undergone
10 grain size selection; and
wherein in the step of adding the molasses binder, the molasses
binder is added by an amount of 5-15 parts by weight.
8. The method of claim 1, wherein in the step of drying the mixed
15 coals and performing a secondary grain size selection to the mixed coals,
the water contents of the mixed coals are controlled to be 4-10wt% of the
mixed coals.
9. The method of claim 1, wherein in the step of manufacturing coal
20 briquettes, the coal briquettes have 20-40% volatile matter contents, 20% or
less coal ash contents and 45-70% fixed carbon contents on a dry basis.
10. The method of claim 9, wherein in the step of manufacturing coal
briquettes, the coal briquettes contain 50% or less SiO2.
25
11. The method of claim 1, wherein in the step of manufacturing coal
briquettes, the coal briquettes have 80% or more coal briquettes of 10mm or
greater in a cold strength evaluation method,
where the cold strength evaluation method is performed by allowing
30 2kg of a sample ore to undergo a free fall from a height of 5m onto a steel
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plate four times and measuring the grain size of the remaining coal
briquettes.
12. The method of claim 1, wherein in the step of manufacturing coal
5 briquettes, the coal briquettes have 60% or more char with a grain size of
15mm or greater in a hot strength evaluation method,
where the hot strength evaluation method is performed by passing
nitrogen gas in a reactor furnace set at 1000°C to obtain char in an inert
atmosphere, and measuring the grain size of the char.
10
13. A method for manufacturing molten irons in which a coal-packed
bed is formed by using coals and reduced irons that have undergone
preliminary reduction is charged into the coal-packed bed, the method
comprising the steps of:
15 performing an initial grain size selection of a first coal group to
prepare fine coals;
mixing a second coal group having a mean reflectance (Rm) of 0.8
or higher into the fine coals;
drying mixed coals comprising the fine coals of the first coal group
20 and the second coal group, and performing a secondary grain size selection
to the mixed coals;
adding a hardening agent to the mixed coals and mixing the
hardening agent and the mixed coals;
adding a molasses binder to the mixed coals and mixing the
25 molasses binder and the mixed coals;
manufacturing coal briquettes by molding the mixed coals;
forming a coal-packed bed using lump coals that have been
separated during the initial grain size selection and the coal briquettes, and
charging reduced irons for mixing into the coal-packed bed; and
30 supplying oxygen to the coal-packed bed to burn coals in the coal-
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packed bed, and manufacturing molten irons by melting reduced irons using
the heat of combustion.
14. The method of claim 13, wherein in the step of wherein in the
5 step of mixing a second coal group into the fine coals, the second coal group
is mixed to 15-80wt% of the mixed coals.
15. The method of claim 13, wherein in the step of drying the mixed
coals and performing a secondary grain size selection to the mixed coals
10 comprising steps of:
drying the mixed coals, and
crushing the mixed coals with a grain diameter exceeding 4mm
among the dried mixed coals such that a grain diameter of the mixed coals
become 4mm or less are selected.
15
16. The method of claim 13, wherein in the step of adding a
hardening agent, one or more hardening agents are selected from the group
consisting of quicklime, slaked lime, limestone, calcium carbonate, cement,
bentonite, clay, silica, silicate, dolomite, phosphoric acid, sulfuric acid, and
20 an oxide.
17. The method of claim 13, wherein in the step of adding a
hardening agent, the hardening agent is added by an amount of 1-5 parts by
weight of 100 parts by weight of the mixed coals that have been dried and
25 undergone grain size selection; and
wherein in the step of adding the molasses binder, the molasses
binder is added by an amount of 5-15 parts by weight.
18. The method of claim 13, wherein in the step of adding molasses
30 binder, molasses binder with a solid content of 70-85wt% is added.
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19. The method of claim 13, wherein in the step of manufacturing
coal briquettes, the coal briquettes have 20-40% volatile matter contents,
20% or less coal ash contents and 45-70% fixed carbon contents on a dry
5 basis.
20. The method of claim 19, wherein in the step of manufacturing
coal briquettes, the coal briquettes contain 50% or less SiO2.
10 21. The method of claim 13, wherein in the step of manufacturing
coal briquettes, the volume of the coal briquette is 10-50cm3.
22. The method of claim 13, wherein in the step of manufacturing
coal briquettes, the coal briquettes have 80% or more coal briquettes of
15 10mm or greater in cold strength evaluation method,
where the cold strength evaluation method is performed by allowing
2kg of a sample ore to undergo a free fall from a height of 5m onto a steel
plate four times and measuring the grain size of the remaining coal
briquettes.
20
23. The method of claim 13, wherein in the step of manufacturing
coal briquettes, the coal briquettes have 60% or more char with a grain size
of 15mm or greater in a hot strength evaluation method,
where the hot strength evaluation method is performed by passing
25 nitrogen gas in a reactor furnace set at 1000°C to obtain char in an inert
atmosphere, and measuring the grain size of the char.
24. The method of claim 13, wherein in the step of forming the coal-
packed bed, the coal briquettes are in the range of 20-80wt% of coals used
30 to form the coal-packed bed.
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25. The method of claim 13, wherein in the step of manufacturing
molten irons, the amount of dissolved Si content in the molten irons is 1wt%
or less.
5
26. The method of claim 13, further comprising a step of recycling
fine coals generated during manufacturing the coal briquettes, and mixing
the fine coals and the mixed coals.
10 27. The method of claim 13, wherein in the step of manufacturing
molten irons, reduced irons manufactured by performing preliminary
reduction of lump iron ores and additives are charged.
28. The method of claim 13, wherein in the step of manufacturing
15 molten irons, iron ores of a small size and additives are preliminary reduced
and hot compacted, and then reduced irons are charged.
29. An apparatus for manufacturing molten irons in which coals and
reduced irons that have undergone preliminary reduction are charged into a
20 melter-gasifier to manufacture molten irons, the apparatus comprising:
a grain size selector for performing an initial grain size selection of a
first coal group;
a coal storage bin for supplying a second coal group having a mean
reflectance of 0.8 or greater, the coal storage bin performing this operation
25 separately from the grain size selector;
a pretreating unit connected to the grain size selector and the coal
storage bin, and drying and performing a secondary selection while mixing
the fine coals of the first coal group and the second coal group;
at least one mixer connected to the pretreating unit, and taking a
30 molasses binder and a hardening agent for mixing with the mixed coals in
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which the fine coals of a first coal group and the second coal group are
mixed;
a roll press connected to the mixer for molding the mixed coals; and
a melter-gasifier connected to the grain size selector and the roll
5 press, and charged with lump coals separated from the grain size selector,
the coal briquettes molded in the roll press, and the reduced irons, and
manufacturing molten irons while being supplied with oxygen.
30. The apparatus of claim 29, further comprising:
10 a binder bin for supplying molasses binder; and
a hardening agent bin for supplying one or more hardening agents
selected from the group consisting of quicklime, slaked lime, limestone,
calcium carbonate, cement, bentonite, clay, silica, silicate, dolomite,
phosphoric acid, sulfuric acid, and an oxide,
15 wherein the binder bin and the hardening agent bin are connected to
the mixer.
31. The apparatus of claim 29, wherein the pretreating unit
comprises:
20 a drier connected to the grain size selector and the coal storage bin,
and drying the mixed coals in which the fine coals of a first coal group and
the second coal group are mixed;
another grain size selector for selecting coals having a grain
diameter of 4mm or less from the drier, and transporting the coals to the
25 mixer; and
a crusher for crushing coals having a grain diameter that exceeds
4mm that have undergone grain size selection.
32. The apparatus of claim 29, wherein the mixer includes a kneader
30 for kneading the mixed coals and the molasses binder.
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33. The apparatus of claim 29, further comprising a recycling
assembly connected to the roll press and the mixer, and collecting fine coals
generated during manufacturing coal briquettes, and supplying the fine coals
5 to the mixer.
34. The apparatus of claim 29, further comprising coal briquette
storage bin connected to the roll press, for temporarily storing the coal
briquettes molded in the roll press.
10
41

The present invention relates to method for manufacturing coal briquettes directly using coals with wide range of grain size, and the method and the apparatus for manufacturing molten irons using the same. For this, the method for manufacturing coal briquettes of the present invention comprises a step of performing an initial grain size selection of a first coal group to prepare fine coals; a step of mixing a second coal group having a mean reflectance (Rm) of 0.8 or higher into the fine coals; a step of drying mixed coals comprising the fine coals of the first coal group and the second coal group, and performing a secondary grain size selection to the mixed, coals; a step of adding a hardening agent to the mixed coals and mixing the hardening agent and the mixed coals; a step of adding a molasses binder to the mixed coals and mixing the molasses binder and the mixed coals; and a step of manufacturing coal briquettes by molding the mixed coals.