CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority to and the benefit of Korean Patent
Application No. 10-2014-0183610 filed in the Korean Intellectual Property Office
on December 18, 2014, the entire contents of which are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to coal briquettes for manufacturing
molten iron, and a method and an apparatus for manufacturing the same.
(b) Description of the Related Art
Blast furnace ironmaking using sintered ore obtained by agglomerating
ore powder, coal power, and cokes has a problem such as a burden of
investment for equipment for limits in quality of available raw materials and fuel,
and environmental regulations.
As an example for overcoming the problem, a method and an apparatus
for directly manufacturing molten iron using reduced agglomerated iron have
been disclosed in U.S. Patent Nos. 4,409,023 and 5, 534,046. Herein, the
apparatus for manufacturing molten iron includes a melting-gasifying furnace
connected with a packed bed type or a fluidized bed type of reduction furnace.
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Reduction iron that has not been reduced in a reduction furnace is reduced and
melted in the melting-gasifying furnace, thereby producing molten iron. In this
case, the coal supplied into the melting-gasifying furnace forms a packed bed
and a reduced gas produced in this process is supplied to the packed bed type
or a fluidized bed type of reduction furnace.
Various reactions such as a gasification reaction of coal described
above, a reduction reaction of non-reduced iron, a combustion reaction at the
front of a tuyere, a slag creation reaction, and other reactions occur in the
packed bed in the melting-gasifying furnace, and heat exchange is generated
between a charged material dropped from above and a rising gas. Porosities
of the packed bed in the melting-gasifying furnace are required to be maintained
for smooth generation of the chemical reactions and the heat transfer. In U.S.
Patent Nos. 4,409,023 and 5,534,046, the grain sizes of the coal put into a
melting-gasifying furnace are limited to 8 to 35 mm. However, when coal is
mined and processed, generally, the amount of lump coal having a grain size of
8 mm or more is small and the lump coal has a disadvantage that the content of
ash is large in comparison to coal powder. Accordingly, this method still has a
problem that coking coal is not efficiently used in the process of producing
molten iron.
In order to solve this problem, U.S. Patent No. 6,332,911 discloses a
method of using pulverized coal in a melting-gasifying furnace. In detail, in
coking coal having the same components and properties, lump coal of 8 mm or
more is directly put into a melting-gasifying furnace and pulverized coal of 8 mm
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or less is formed into compacted iron over a predetermined size, with bitumen
as a binder, and put into a melting-gasifying furnace. However, in this method,
it is required to consider not only the characteristics of the lump coal of 8 mm or
more from the same coking coal, but the characteristics of coal briquettes from
coal powder of 8 mm or less with bitumen used as a binder, so it is very difficult
to select the types of coal for controlling the characteristics of a packed bed in
the melting-gasifying furnace and the controllable range is very limited.
Further, the price of a bitumen binder is proportional to the oil price, so the price
is high, and the binder is easily thermally decomposed around the dome of a
melting-gasifying furnace maintained at a temperature of about 1000 C, so it
has a fundamental problem of deterioration of binding ability of coal powder.
In order to solve these problems, a technology of manufacturing coal
briquettes after mixing several kinds of coal, using various hardeners based on
a molasses binder, has been disclosed in Korean Patent Laid-Open Publication
No. 2004-0004738. In this case, mixing of coal, selection of a hardener, and
the volume of coal briquettes, which can improve the efficiency of a packed bed
in a melting-gasifying furnace, and a process capable of variously controlling
them, have been disclosed.
However, in this method, it is required to develop an additional control
unit that increases the amount of production of molten iron by increasing
efficiency of a melting-gasifying furnace in the process of producing molten iron
using manufactured coal briquettes, and that provides an economical process
by reducing necessary fuel cost. To this end, it is required to reduce the
amount of degradation of coal briquettes in a melting-gasifying furnace, so gas
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and liquid can smoothly pass in the melting-gasifying furnace by coal briquettes
having large grain sizes, and accordingly, performance of passing air and liquid
is ensured and reaction efficiency and heat transfer efficiency can be increased.
Further, it may be possible to reduce the amount of powder that is produced by
the degradation and not efficiently used in the process.
Several methods have been proposed to reduce degradation of coal
briquettes in a melting-gasifying furnace. For example, a method of adding
coke dust or sludge that is a byproduct in a process of manufacturing cokes has
been disclosed in Korean Patent Laid-Open Publication No. 2012-0151311, a
method of adding graphite has been disclosed in Korean Patent Laid-Open
Publication No. 2012-0155437, and a method of forming carbon sources such
as various kinds of coal or coal cokes at a high temperature over 800 C and
mixing them in the process of forming coal briquettes has been disclosed in
Korean Patent Laid-Open Publication No. 2012-0151312, and they achieved an
effect of largely suppressing degradation of coal briquettes at a high
temperature.
However, the technologies disclosed in Korean Patent Laid-Open
Publication Nos. 2012-0151311 and 2012-0155437 have a drawback that a raw
material is difficult to ensure and is expensive. Further, the technology
disclosed in Korean Patent Laid-Open Publication No. 2012-0151312 has a
problem in that a specific forming process is required and accordingly the
manufacturing cost increases.
The above information disclosed in this Background section is only for
enhancement of understanding of the background of the invention and therefore
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it may contain information that does not form the prior art that is already known
in this country to a person of ordinary skill in the art.
SUMMARY OF THE INVENTION
An embodiment of the present invention has been made in an effort to
provide coal briquettes for manufacturing molten iron having excellent hot
quality by adding anthracite that is thermally stable due to a high degree of
coalification.
Another exemplary embodiment of the present invention provides a
method and an apparatus for manufacturing coal briquettes for manufacturing
molten iron having excellent hot quality by adding anthracite that is thermally
stable due to a high degree of coalification.
An exemplary embodiment of the present invention provides coal
briquettes that are put into a dome of a melting-gasifying furnace in an
apparatus for manufacturing molten pig iron, which includes a melting-gasifying
furnace receiving reduced iron and a reduction furnace connected to the
melting-gasifying furnace and providing the reduced iron, and that include a first
mixture including anthracite at over 0 wt% to 30 wt%, and the balance of coal
powder.
The grain size of the anthracite may be over 0 mm and 5 mm or less.
The anthracite may include meta-anthracite.
The coal briquettes may further include a hardener, and the hardener is
included at 1 to 5 parts by weight with respect to a first mixture of 100 parts by
weight.
The hardener may be one or more substances selected from a group of
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quicklime, slaked lime, limestone, calcium carbonate, cement, bentonite, clay,
silica, silicate, dolomite, phosphoric acid, sulfuric acid, and oxides.
The coal briquettes may further include a binder at 5 to 15 parts by
weight with respect to a first mixture of 100 parts by weight.
The binder may be one or more substances selected from a group of
molasses, bitumen, asphalt, coal tar, pitch, starch, water glass, plastic, polymer
resin, and oil.
A hot strength index of the coal briquettes may be 70 % or more.
Another exemplary embodiment of the present invention provides a
method of manufacturing coal briquettes that includes: preparing anthracite;
preparing coal powder; preparing a first mixture produced by mixing the
anthracite and the coal powder; and obtaining coal briquettes by forming the
first mixture, in which the first mixture includes anthracite at over 0 wt% to 30
wt% and the balance of coal powder.
The preparing of a first mixture produced by mixing the anthracite and
the coal powder and the obtaining of coal briquettes by forming the first mixture
may be preparing a first mixture produced by mixing the anthracite and the coal
powder, manufacturing a second mixture produced by mixing a hardener, a
binder, of a combination thereof with the first mixture, and obtaining coal
briquettes by forming the second mixture.
The hardener may be 1 to 5 parts by weight with respect to the first
mixture of 100 parts by weight.
The hardener may be one or more substances selected from a group of
quicklime, slaked lime, limestone, calcium carbonate, cement, bentonite, clay,
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silica, silicate, dolomite, phosphoric acid, sulfuric acid, and oxides. The binder
may be 5 to 15 parts by weight with respect to the first mixture of 100 parts by
weight.
The binder may be one or more substances selected from a group of
molasses, bitumen, asphalt, coal tar, pitch, starch, water glass, plastic, polymer
resin, and oil.
In the obtaining of coal briquettes by forming the first mixture, the
forming may be performed by compressing with a roll press.
In the preparing of anthracite, the grain size of the anthracite may be
over 0 mm and 5 mm or less.
The anthracite may include meta-anthracite.
A hot strength index of the obtained coal briquettes may be 70 % or
more.
Yet another exemplary embodiment of the present invention provides an
apparatus for forming coal briquettes that includes: an anthracite storage that
stores anthracite; an anthracite conveying pipe that is connected to the
anthracite storage and conveys the anthracite to the anthracite storage; a coal
powder storage that stores coal powder; a binder storage that stores a binder; a
hardener storage that stores a hardener; a mixer that provides a mixture by
mixing anthracite from the anthracite storage, coal powder from the coal powder
storage, a binder from the binder storage, and a hardener from the hardener
storage; and a molding machine that forms a mixture using the mixture from the
mixer.
The anthracite storage may be directly connected with the mixer.
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According to an exemplary embodiment of the present invention, it is
possible to provide coal briquettes for manufacturing molten iron having
excellent quality in hot processes by adding anthracite that is thermally stable
due to a high degree of coalification.
According to another exemplary embodiment of the present invention, it
is possible to provide a method and an apparatus for manufacturing coal
briquettes for manufacturing molten iron having excellent quality in hot
processes by adding anthracite that is thermally stable due to a high degree of
coalification.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram illustrating an apparatus for
manufacturing coal briquettes according to an embodiment.
FIG. 2 is a schematic view illustrating an apparatus for manufacturing
molten iron, using coal briquettes manufacturing by the apparatus for
manufacturing coal briquettes illustrated in FIG. 1.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Hereinafter, exemplary embodiments of the present invention will be
described. The exemplary embodiments, however, are provided as examples,
and the present invention is not limited thereto, but is defined within the range of
claims to be described below.
Throughout the specification, unless explicitly described to the contrary,
the word “comprise” and variations such as “comprises” or “comprising” will be
understood to imply the inclusion of stated elements but not the exclusion of
any other elements.
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An embodiment of the present invention provides coal briquettes that
are put into the dome of a melting-gasifying furnace in an apparatus for
manufacturing molten iron, which includes a melting-gasifying furnace receiving
reduced iron and a reduction furnace connected to the melting-gasifying furnace
and providing the reduced iron, and that include a first mixture including
anthracite at over 0 wt% to 30 wt% and the balance of coal powder.
The coal briquettes according to an embodiment of the present invention
include a first mixture.
In detail, the first mixture of the coal briquettes according to an
embodiment of the present invention includes anthracite.
The anthracite has the highest degree of coalification in coals, so it has
high thermal conductivity and low thermal expansion. Using these
characteristics, it is possible to ensure thermal stability and reduce thermal
degradation of coal briquettes due to thermal shock and discharge of a volatile
matter when putting the coal briquettes into the dome of a melting-gasification
furnace at a high temperature and rapidly heating them.
In detail, while the coal material that is the main component of coal
briquettes undergoes softening-melting and re-solidifying in the process of
being rapidly heated at a high-temperature portion of a melting-gasifying
furnace, it is cracked by expansion and contraction, but anthracite can relatively
stably exist even in this temperature change process.
Further, anthracite is a kind of coal having the highest degree of
coalification, so it includes a small amount of water and volatile matter and
includes a relatively large amount of fixed carbon, and accordingly, the amount
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of a volatile matter causing degradation in the process of discharging is
relatively small and the amount of gasification is small. Therefore, it is possible
to increase the amount of coal briquettes flowing into the lower portion of a
melting-gasifying furnace in a solid state. Further, anthracite has an economic
advantage in that it is inexpensive relative to bituminous coal for manufacturing
other cokes.
An embodiment of the present invention may include the anthracite at
over 0 wt% to 30 wt%. When the content of the anthracite exceeds 30 wt%,
the hot strength index exhibiting hot quality reduces as compared with
anthracite that is not mixed. Accordingly, the content of anthracite is adjusted
within the range described above.
In an embodiment of the present invention, the grain size of the
anthracite may be over 0 mm to 5 mm, in detail, over 0 mm to 3 mm. When
the grain size of the anthracite exceeds 5 mm, the hot quality of coal briquettes
is deteriorated, so the grain size of the anthracite is limited within the range
described above.
In the specification, the “grain size” means the diameter of a grain when
the grain has a spherical shape, but it means the average of the diameters in
predetermined directions, when the grain has a complicated shape.
In an embodiment of the present invention, the anthracite may include
meta-anthracite that has larger degree of coalification than common anthracite.
The first mixture of the coal briquettes according to an embodiment of
the present invention includes coal powder.
In an embodiment of the present invention, the coal powder may be
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included at 70 wt% or more and less than 100 wt%. However, the content of
the coal powder is determined as the amount except for the content of the
anthracite, so it is not limited thereto.
The coal powder may be provided by sorting grain sizes of coking coal.
For example, coking coal having a grain size of 8 mm or less may be provided
as the coal powder. That is, coking coal can be separately supplied as coal
powder having a small grain size and lump coal having a large grain size by
sorting the grain sizes of the coking coal. Using coal powder having a small
grain size as coking coal makes it possible to manufacture coal briquettes
having excellent cold strength. Lump coal that is coking coal having a grain
size exceeding 8 mm can be directly put into a melting-gasifying furnace or
used after being broken. On the other hand, coal for adjusting quality may be
mixed with coal powder to improve the quality of molten iron. Herein, as the
coal for adjusting quality, coal having a reflection ratio over a predetermined
level may be used.
On the other hand, it may not be possible to provide a necessary
binding force for forming an agglomerated matter at room temperature only from
the main components of the coal briquettes, that is, anthracite and coal powder.
In this case, the coal briquettes according to an embodiment of the
present invention may further include a hardener, a binder, or a combination
thereof.
In detail, if the amount of the first mixture is 100 parts by weight, the coal
briquettes according to an embodiment of the present invention may further
include a hardener at 1 to 5 parts by weight. Herein, the hardener may be one
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or more substances selected from a group of quicklime, slaked lime, limestone,
calcium carbonate, cement, bentonite, clay, silica, silicate, dolomite, phosphoric
acid, sulfuric acid, and oxides, but is not limited thereto. Too small an amount
of hardener causes insufficient chemical binding of a binder and a hardener,
which is described below, so sufficient strength of coal briquettes cannot be
ensured. Further, too large an amount of hardener increases ash in coal
briquettes, so it cannot sufficiently function as a fuel in a melting-gasifying
furnace. Accordingly, the content of the hardener is adjusted within the range
described above.
Further, if the amount of the first mixture is 100 parts by weight, the coal
briquettes according to an embodiment of the present invention may further
include a binder at 5 to 15 parts by weight. The binder may be one or more
substances selected from a group of molasses, bitumen, asphalt, coal tar, pitch,
starch, water glass, plastic, polymer resin, and oil, but is not limited thereto.
Too small an amount of binder may decrease the strength of coal briquettes.
Too large an amount of binder causes sticking when pulverized coal and a
binder are mixed. Accordingly, the content of the binder is adjusted within the
range described above.
Another exemplary embodiment of the present invention provides a
method of manufacturing coal briquettes that includes: preparing anthracite;
preparing coal powder; preparing a first mixture produced by mixing the
anthracite and the coal powder; and obtaining coal briquettes by forming the
first mixture, in which the first mixture includes anthracite at over 0 wt% to 30
wt% and the balance of coal powder.
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In more detail, the preparing of a first mixture produced by mixing the
anthracite and the coal powder and the obtaining of coal briquettes by forming
the first mixture in another exemplary embodiment of the present invention may
be preparing a first mixture produced by mixing the anthracite and the coal
powder, manufacturing a second mixture produced by mixing a hardener, a
binder, of a combination thereof with the first mixture, and obtaining coal
briquettes by forming the second mixture.
In this case, if the amount of the first mixture is 100 parts by weight, the
hardener may be included at 1 to 5 parts by weight. Herein, the hardener may
be one or more substances selected from a group of quicklime, slaked lime,
limestone, calcium carbonate, cement, bentonite, clay, silica, silicate, dolomite,
phosphoric acid, sulfuric acid, and oxides, but is not limited thereto. Too small
an amount of hardener causes insufficient chemical binding of a binder and a
hardener, which is described below, so sufficient strength of coal briquettes
cannot be ensured. Further, too large an amount of hardener increases ash in
coal briquettes, so it cannot sufficiently function as a fuel in a melting-gasifying
furnace. Accordingly, the content of the hardener is adjusted within the range
described above.
Further, if the amount of the first mixture is 100 parts by weight, the
binder may be included by 5 to 15 parts by weight. Herein, the binder may be
one or more substances selected from a group of molasses, bitumen, asphalt,
coal tar, pitch, starch, water glass, plastic, polymer resin, and oil, but is not
limited thereto. Too small an amount of binder may decrease the strength of
coal briquettes. Too large an amount of binder causes sticking when
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pulverized coal and a binder are mixed. Accordingly, the content of the binder
is adjusted within the range described above.
In the obtaining of coal briquettes by forming the first mixture in another
exemplary embodiment of the present invention, the forming may be performed
by compressing with a roll press.
In the preparing of anthracite for suppressing high-temperature
degradation of the coal briquettes, the grain size of the anthracite may be larger
than 0 mm and 5 mm or less.
The anthracite may include meta-anthracite that has larger degree of
coalification than common anthracite.
The obtaining of coal briquettes by forming the first mixture or/and the
obtaining of coal briquettes by forming the second mixture in another exemplary
embodiment of the present invention is not illustrated in the figures, but pocketor
strip-type coal briquettes may be manufactured by putting a mixture between
a pair of rolls rotating in opposite directions.
Another exemplary embodiment of the present invention provides an
apparatus for forming coal briquettes that includes: an anthracite storage that
stores anthracite; an anthracite conveying pipe that is connected to the
anthracite storage and conveys the anthracite to the anthracite storage; a coal
powder storage that stores coal powder; a binder storage that stores a binder; a
hardener storage that stores a hardener; a mixer that provides a mixture by
mixing anthracite from the anthracite storage, coal powder from the coal powder
storage, a binder from the binder storage, and a hardener from the hardener
storage; and a molding machine that forms a mixture using the mixture from the
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mixer.
FIG. 1 is a schematic diagram illustrating an apparatus 100 for
manufacturing coal briquettes according to yet another exemplary embodiment
of the present invention.
Referring to FIG. 1, the apparatus 100 for manufacturing coal briquettes
includes a coal powder storage 10, an anthracite storage 20, an anthracite
conveying pipe 30, a binder storage 40, a hardener storage 50, a mixer 60, and
a molding machine 70. Further, the apparatus 100 for manufacturing coal
briquettes further include a breaker 80, a drier 90, a mixed coal storage 92, a
returned coal storage 94, and grain size sorters 801, 803, and 805. If
necessary, the apparatus 100 for manufacturing coal briquettes may further
include other units. Detailed structures and operations of the components of
the apparatus 100 for manufacturing coal briquettes in FIG. 1 can be easily
understood by those skilled in the art, so they are not described in detail.
The coal powder storage 10 stores coal powder. Coal for adjusting
quality may be used to improve the quality of coal briquettes. In this case,
though not illustrated in FIG. 1, a separate coal storage for adjusting quality
may be used or coal for adjusting quality may be stored in the coal powder
storage 10.
Coal can be separated into lump coal and coal powder through the grain
size sorter 801, and then the coal powder can be stored in the coal powder
storage 10. For example, coal having a grain size of 8 mm or less may be
used as the coal powder. Meanwhile, the lump coal separated by the grain
size sorter 801 may be directly put into a melting-gasifying furnace (not
17
illustrated).
As illustrated in FIG. 1, the anthracite storage 20 may include a first
anthracite storage 201 or/and a second anthracite storage 203.
In detail, not-broken anthracite may be stored in the first anthracite
storage 201 and the stored anthracite is produced into coking coal having a
grain size suitable for manufacturing coal briquettes by being mixed with the
coal powder, dried, and broken.
Since the anthracite of which the grain size is adjusted by being broken
through a specific breaker is stored in the second anthracite storage 203, it can
be mixed with a binder and a hardener in the mixer 60 without pretreatment.
The anthracite conveying pipe 30 may include a first anthracite
conveying pipe 303 or/and a second anthracite conveying pipe 301. The first
anthracite conveying pipe 303 or/and the second anthracite conveying pipe 301
are connected to the first anthracite storage 201 or/and the second anthracite
storage 203, respectively. For example, anthracite including a large amount of
water can be supplied to the first anthracite storage 201 through a conveyer belt
disposed in the first anthracite conveying pipe 303, and anthracite may be
conveyed under pressure as a gas to the second anthracite storage 203 using
the second anthracite conveying pipe 301. Accordingly, it is possible to quickly
and smoothly supply anthracite when manufacturing coal briquettes.
The drier 90 dries coal powder and anthracite. That is, the coal powder
from the coal powder storage 10 and the anthracite from the anthracite storage
20 are dried through the drier 90. The amount of water is appropriately
controlled by hot air while the coal power and the anthracite are mixed in the
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drier 90.
Mixed coal is separated by the grain size sorter 803, and mixed coal
having a predetermined grain size or more is broken by the breaker 80. The
broken mixed coal and the mixed coal having a grain size of less than a
predetermined level are stored in the mixed coal storage 92. The mixed coal
stored in the mixed coal storage 92 is provided to the mixer 60.
As illustrated in FIG. 1, a binder is stored in the binder storage 40. The
binder is made in a state suitable for manufacturing coal briquettes by mixing
coal powder and anthracite. The binder storage 40 is connected with the mixer
60 and provides a binder to the mixer 60.
Meanwhile, a hardener is stored in the hardener storage 50. The
strength of the hardened coal briquettes can be optimized by hardening them by
bonding the coal powder, anthracite, and binder. The hardener storage 50 is
connected with the mixer 60 and provides a hardener to the mixer 60.
The mixer 60 provides a mixture for manufacturing coal briquettes by
mixing coal powder, anthracite, a binder, and a hardener. Meanwhile, the
second anthracite storage 203 may be connected directly with the mixer 60 and
directly supply anthracite to the mixer 60. In this case, the anthracite supplied
through the second anthracite storage 203 is controlled in the amount of water
and the grain size, so it can be directly used by the mixer 60.
As illustrated in FIG. 1, the molding machine 70 includes a pair of rolls
rotating in opposite directions. A mixture is supplied between the pair of rolls
and compressed by the pair of rolls, thereby manufacturing coal briquettes.
Meanwhile, the manufactured coal briquettes are separated again through the
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grain size sorter 805, and the coal powder is stored in the returned coal storage
94. The coal powder stored in the returned coal storage 94 is supplied back to
the mixer 50 and can be used as the raw material of coal briquettes. As a
result, usability of coal powder can be improved.
Coal briquettes manufactured at room temperature are put into the
dome over a packed bed in a melting-gasifying furnace maintained at a high
temperature of about 1000 C, and then rapidly heated.
FIG. 2 schematically illustrates an apparatus 200 for manufacturing
molten iron that is connected with the apparatus 100 for manufacturing coal
briquettes and uses the coal briquettes manufactured by the apparatus 100 for
manufacturing coal briquettes.
Referring to FIG. 2, the apparatus 200 for manufacturing molten iron
includes a melting-gasifying furnace 210 and a reduction furnace 220. Further,
the apparatus 200 for manufacturing molten iron may include other units, if
necessary.
Iron ore is put into and reduced in the reduction furnace 220. Iron ore
put into the reduction furnace 220 is manufactured into reduced iron through the
reduction furnace 220 after being dried in advance. The reduction furnace 220
is a packed bed type of reduction furnace, and forms a packed bed therein by
receiving reduction gas from the melting-gasifying furnace 210.
The coal briquettes manufactured by the apparatus 100 for
manufacturing coal briquettes illustrated in FIG. 1 are put into the meltinggasifying
furnace 210 illustrated in FIG. 2, so a coal packed bed is formed in the
melting-gasifying furnace 210. A dome 2101 is formed at the upper portion of
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the melting-gasifying furnace 210. High-temperature reduction gas exists in
the dome 2101 formed wider than other portions of the melting-gasifying
furnace 210. Coal briquettes are put into the dome 2101 of the meltinggasifying
furnace 210, and then rapidly heated and dropped to the bottom of the
melting-gasifying furnace 210. Char created by thermal decomposition of coal
briquettes moves to the bottom of the melting-gasifying furnace 210 and then
exothermic-reacts with oxygen supplied through a tuyere 230. As a result, the
coal briquettes can be used as a heat source maintaining the melting-gasifying
furnace 210 at a high temperature. Meanwhile, the char provides air
permeability, so a large amount of gas produced at the lower portion of the
melting-gasifying furnace 210 and the reduced iron supplied from the reduction
furnace 220 can be more easily and uniformly passed through the coal packed
bed in the melting-gasifying furnace 210.
Meanwhile, in this process, the coal briquettes receive thermal shock,
and cracking and breaking are generated while the volatile components in the
coal briquettes are rapidly discharged, so they are degraded.
While coal briquettes degraded into small sizes remain at the lower
portion of the melting-gasifying furnace, it is required for the grain size of the
stored coal briquettes to be large in order to smoothly pass a rising gas and
enable molten iron or slag that is melted and dropping to smoothly flow.
In order to store coal briquettes having a relatively large grain sizes in
the melting-gasifying furnace, it is required to maintain hot quality, which
suppresses easy degradation at a high temperature, as an important quality
index. Hot degradation factors of the coal briquettes that influence the hot
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quality are as follows.
The first is a temperature difference, that is, a temperature gradient
between the inside and the outside of coal briquettes. This factor causes early
stage degradation such as cracks due to differences in contraction and
expansion of coal briquettes, which are coal-formed matters.
Second, volatile components in a coal mixture cause a defect in the
structure of coal briquettes while they are expanded by rapid heating and
rapidly discharged out of the coal briquettes. One of methods of suppressing
high-temperature degradation of coal briquettes is to reduce the reason of
degradation by adding a substance that is thermally stable at a high
temperature such as a carbon source molded at a high temperature, or
anthracite or graphite, when manufacturing coal briquettes.
According to the present invention, it is possible to reduce the reason of
degradation, to ensure thermal stability when coal briquettes are put into the
dome of a melting-gasifying furnace at a high temperature and rapidly heated
and when thermal shock is applied and volatile components are discharged, by
adding anthracite that can be easily obtained at a low cost, and to reduce
thermal degradation of coal briquettes.
Hereinafter, exemplary embodiments of the present invention and
comparative examples are described. However, the following exemplary
embodiments are just examples of the present invention and the present
invention is not limited to those exemplary embodiments.
Exemplary embodiment
Exemplary Embodiment 1
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95 wt% of coal including volatile matter, ash, and fixed carbon of which
the contents are as in [Table 1] and anthracite at 5 wt% were mixed. The grain
size of 5 mm or less of the coal and the anthracite was measured as 90 %.
(Table 1)
(unit: %)
Volatile matter Ash Fixed carbon
Coal 22.2 9.6 68.2
Anthracite 5.3 16.6 80.0
Quicklime at 3 parts by weight as a hardener and molasses at 8 parts by
weight as a binder were mixed with the mixture of 100 parts by weight.
The fixed raw materials were uniformly mixed in a mixing test device
and then manufactured into coal briquettes by a double roll press.
Exemplary Embodiment 2
Coal briquettes were manufactured as in Exemplary Embodiment 1,
except that coal at 90 wt% and anthracite at 10 wt% were mixed.
Exemplary Embodiment 3
Coal briquettes were manufactured as in Exemplary Embodiment 1,
except that coal at 85 wt% and anthracite at 15 wt% were mixed.
Exemplary Embodiment 4
Coal briquettes were manufactured as in Exemplary Embodiment 1,
except that coal at 80 wt% and anthracite at 20 wt% were mixed.
Exemplary Embodiment 5
Coal briquettes were manufactured as in Exemplary Embodiment 1,
23
except that coal at 75 wt% and anthracite at 25 wt% were mixed.
Exemplary Embodiment 6
Coal briquettes were manufactured as in Exemplary Embodiment 1,
except that coal at 70 wt% and anthracite at 30 wt% were mixed.
Exemplary Embodiment 7
Coal briquettes were manufactured as in Exemplary Embodiment 2,
except that anthracite including the volatile matter, ash, and fixed carbon
proposed in [Table 2] was used instead of the anthracite proposed in [Table 1]
in Exemplary Embodiment 2.
(Table 2)
(unit: %)
Volatile matter Ash Fixed carbon
Anthracite 5.8 17.3 76.9
Exemplary Embodiment 8
Coal briquettes were manufactured as in Exemplary Embodiment 7,
except that coal at 70 wt% and anthracite at 30 wt% were mixed.
Exemplary Embodiment 9
Coal briquettes were manufactured as in Exemplary Embodiment 2,
except that meta-anthracite including the volatile matter, ash, and fixed carbon
proposed in [Table 3] was used instead of the anthracite proposed in [Table 1]
in Exemplary Embodiment 2.
(Table 3)
(unit: %)
24
Volatile matter Ash Fixed carbon
Meta-anthracite 4.4 9.1 86.5
Exemplary Embodiment 10
Coal briquettes were manufactured as in Exemplary Embodiment 9,
except that coal at 70 wt% and anthracite at 30 wt% were mixed.
Comparative Example 1
Coal briquettes were manufactured as in Exemplary Embodiment 1,
except that coal at 100 wt% was used.
Comparative Example 2
Coal briquettes were manufactured as in Exemplary Embodiment 1,
except that coal t 60 wt% and anthracite T 40 wt% were mixed.
Estimation
Estimation 1: Cold quality estimation
Cold quality means strength quality at room temperature with respect to
various physical degradation conditions that can be applied while manufactured
coal briquettes are conveyed and stored directly before being put into a meltinggasifying
furnace, and it is estimated using a drop strength index.
The drop strength index is illustrated by weight percentage of a grain
size over 20 mm after a coal briquette sample of 2 kg was freely dropped four
times from a height of 5 m.
Estimation 2: Hot quality estimation
Hot quality means quality that can resist various physical, chemical, and
thermal conditions that can be applied to room-temperature coal briquettes in a
melting-gasifying furnace at a high temperature, and it is estimated using a hot
25
strength index.
The hot strength index typically standardizes degradation in rapid
heating and degradation due to wear between particles that have the largest
influence in a behavior of degradation of coal briquettes in a melting-gasifying
furnace.
A room-temperature coal briquette sample of 1000 g was put into a
reaction pipe increased to a temperature of 1000 C and rotated at the
temperature and then reacted at 10 rpm for 60 min. The reaction gas was inert
nitrogen, and the temperature of the reaction pipe was maintained at 1000 C
during the reaction. The hot strength index of coal briquettes was exhibited by
analyzing the grain sizes of coal briquette char created after the reaction and
then expressing the weight of that over 10 mm as a percentage with respect to
the weight of the total coal briquette char. That is, coal briquettes of which the
hot strength indexes were estimated to be high were relatively less degraded by
rapid thermal shock and wear between particles in the dome of the meltinggasifying
furnace, so it can be determined that char having a large grain size
may exist in the packed bed in the melting-gasifying furnace.
Estimation result
Result 1: Engineering analysis result
The result of engineering analysis (ISO 17246:2010, Coal Proximate
Analysis) of the coal briquettes manufactured in Exemplary Embodiments 1, 2,
4, and 6 and Comparative Examples 1 and 2 are listed in [Table 4].
(Table 4)
26
Mixture Combination
Ratio (wt%)
Engineering Analysis (%)
Coal Anthracite Volatile Matter Ash Fixed Carbon
Exemplary
Embodiment
1
95 5 27.6 12.4 60.0
Exemplary
Embodiment
2
90 10 27.1 12.8 60.1
Exemplary
Embodiment
4
80 20 24.9 13.7 61.4
Exemplary
Embodiment
6
70 30 23.0 14.9 62.2
Comparative
Example 1
100 0 28.8 11.8 59.8
Comparative
Example 2
60 40 21.0 15.8 63.1
Referring to [Table 4], it can be seen that the larger the combination
ratio of the anthracite, the larger the content of the fixed carbon in the coal
briquettes. The larger the content of the fixed carbon in the coal briquette, the
more the solid carbon sources flows into the meting-gasifying furnace, so a
27
function as a useful fuel can be expected.
Result 2: Cold quality estimation result
Drop strength indexes in Exemplary Embodiments 1 to 6 and
Comparative Examples 1 and 2 estimated in accordance with the estimation 1
are listed in [Table 5].
(Table 5)
Mixture Combination Ratio (wt%) Drop Strength Index (%)
Coal Anthracite
Exemplary
Embodiment
1
95 5 96.1
Exemplary
Embodiment
2
90 10 94.3
Exemplary
Embodiment
3
85 15 95.5
Exemplary
Embodiment
4
80 20 94.3
Exemplary
Embodiment
5
75 25 93.9
28
Exemplary
Embodiment
6
70 30 92.1
Comparative
Example 1
100 0 94.8
Comparative
Example 2
60 40 93.4
Referring to [Table 5], it can be seen that as the additional amount of
anthracite increased, the drop strength indexes did not substantially change.
Result 3: Hot quality estimation result
Hot strength indexes in Exemplary Embodiments 1 to 10 and
Comparative Examples 1 and 2 estimated in accordance with the estimation 2
are listed in [Table 6].
(Table 6)
Mixture Combination Ratio (wt%) Hot Strength Index (%)
Coal Anthracite (Metaanthracite)
Exemplary
Embodiment
1
95 5 66.2
Exemplary
Embodiment
2
90 10 70.8
29
Exemplary
Embodiment
3
85 15 73.2
Exemplary
Embodiment
4
80 20 72.9
Exemplary
Embodiment
5
75 25 71.4
Exemplary
Embodiment
6
70 30 66.2
Exemplary
Embodiment
7
90 10 70.4
Exemplary
Embodiment
8
70 30 69.7
Exemplary
Embodiment
9
90 10 73.3
Exemplary
Embodiment
70 30 68.4
30
10
Comparative
Example 1
100 0 65.3
Comparative
Example 2
60 40 48.9
Referring to [Table 6], it can be seen that the hot strength index was
64.2 % in Comparative Example 1 in which anthracite was not mixed, but as the
combination ratio of anthracite increased, the index increased, and the hot
strength index was a maximum of 70 % when the combination ratio of
anthracite was about 15 to 20 wt% , while in Comparative Example 2 in which
the combination ratio was 40 wt%, the hot strength index was lower than that in
Comparative Example 1 without anthracite.
Further, it can be seen that similar results were obtained in Exemplary
Embodiments 7 and 8 using anthracite including a small content of fixed carbon
as compared with Exemplary Embodiments 1 to 6, and in Comparative
Examples 9 and 10 using meta-anthracite.
(2) Coal briquettes were manufactured as in Exemplary Embodiments 1,
2, 4, and 6 and Comparative Examples 1 and 2, anthracite was broken to a
grain size of 3 mm or less, hot quality was estimated in accordance with
estimation 2, and the hot strength indexes are listed in [Table 7].
(Table 7)
Mixture Combination Ratio (wt%) Hot Strength Index (%)
Coal Anthracite
31
Exemplary
Embodiment
1
95 5 68.0
Exemplary
Embodiment
2
90 10 75.3
Exemplary
Embodiment
4
80 20 77.9
Exemplary
Embodiment
6
70 30 70.1
Comparative
Example 1
100 0 65.3
Comparative
Example 2
60 40 49.7
Referring to [Table 7], when the anthracite was broken to a grain size of
3 mm or less, the hot strength index was increased as compared with when it
was estimated for anthracite having a grain size of 5 mm or less. Accordingly,
it may be considered that it is advantageous to break anthracite to a relatively
small grain size and mix it in order to improve the effect of increasing the hot
strength index.
Experimental Example
32
The results found through the exemplary embodiments were directly
applied to a melting-gasifying furnace operated to manufacture molten iron, and
the effects were checked. The melting-gasifying furnace was equipment that
produces molten iron at 800,000 tons per year.
Coal briquettes were manufactured by mixing coal powder having a
grain size of 8 mm or less at 87.4 wt%, quicklime at 2.8 wt%, and molasses at
9.8 wt% that is a liquid-state binder in a mixer, and then molding a mixed raw
material having undergone additional agitation in an agitator with a roll molding
machine.
Thereafter, anthracite was increased step by step to 8 % and 12 % with
respect to the sum of the coal powder and the anthracite, the conditions were
continuously applied for 48 h, and the results of measuring molten iron
temperature and a fuel ratio are listed in [Table 8]. In this case, the
temperature of discharged molten iron was measured by a dipping type of
thermoscope in a runner, and the fuel ratio was estimated by generally
considering and calculating the amount of molten iron used and the amount of
fuel used.
(Table 8)
Anthracite (wt%) 0 8 12
Hot Strength Index (%) 68.4 75.5 78.3
Melting-
Gasifying
Furnace
Molten Iron
Temperature (°C)
1,508 1,512 1,517
33
Operated
Fuel Ratio (t/h) 821 817 815
Referring to [Table 8], considerably improved hot strength indexes can
be achieved, as in the previous exemplary embodiments.
Further, it can be seen that when coal briquettes manufactured with the
increased additive ratio of anthracite were put into a melting-gasifying furnace
that was being actually operated, the molten iron temperature was increased.
This is considered to be caused by improvement of heat transfer efficiency due
to an increase in grain size in the packed bed in the melting-gasifying furnace
according to improvement of hot quality of the coal briquettes.
It is considered that, as the hot quality of coal briquettes was improved,
that is, as the hot strength index was increased, the amount degraded and
consumed in the melting-gasifying furnace was smaller, and as the combination
ratio of anthracite was increased, the content of the fixed carbon in the coal
briquettes was increased (see [Table 4]), so the fuel ratio for producing molten
iron was reduced.
While this invention has been described in connection with what is
presently considered to be practical exemplary embodiments, it is to be
understood that the invention is not limited to the disclosed embodiments, but,
on the contrary, is intended to cover various modifications and equivalent
arrangements included within the spirit and scope of the appended claims.
Therefore, the embodiments described above are only examples and should not
be construed as being limitative in any respects.

34
10: Coal powder storage
20, 201, 203: Anthracite storage
30, 301, 302: Anthracite conveying pipe
40: Binder storage 50: Hardener storage
60: Mixer 70: Molding machine
80: Breaker 90: Drier
92: Mixed coal storage 94: Returned coal storage
100: Apparatus for manufacturing coal briquettes
200: Apparatus for manufacturing molten iron
210: Melting-gasifying furnace
220: Packed bed type reduction furnace 230: Tuyere
801, 803, 805: Grain size sorter
2101: Dome
35

WHAT IS CLAIMED IS:
1. Coal briquettes that are put into a dome of a melting-gasifying
furnace in an apparatus for manufacturing molten pig iron, which includes a
melting-gasifying furnace receiving reduced iron and a reduction furnace
connected to the melting-gasifying furnace and providing the reduced iron, and
that include a first mixture including anthracite at over 0 wt% to 30 wt% and the
balance of coal powder.
2. The coal briquettes of claim 1, wherein
the grain size of the anthracite is over 0 mm and 5 mm or less.
3. The coal briquettes of claim 1, wherein
the anthracite includes meta-anthracite.
4. The coal briquettes of claim 1, further comprising
a hardener,
wherein the hardener is included at 1 to 5 parts by weight with respect to
a first mixture of 100 parts by weight.
5. The coal briquettes of claim 4, wherein
the hardener is one or more substances selected from a group of
quicklime, slaked lime, limestone, calcium carbonate, cement, bentonite, clay,
silica, silicate, dolomite, phosphoric acid, sulfuric acid, and oxides.
36
6. The coal briquettes of claim 1, further comprising
a binder,
wherein the binder is included at 5 to 15 parts by weight with respect to
the first mixture at 100 parts by weight.
7. The coal briquettes of claim 6, wherein
the binder is one or more substances selected from a group of molasses,
bitumen, asphalt, coal tar, pitch, starch, water glass, plastic, polymer resin, and
oil.
8. The coal briquettes of claim 1, wherein
a hot strength index of the coal briquettes is 70 % or more.
9. A method of manufacturing coal briquettes, comprising:
preparing anthracite;
preparing coal powder;
preparing a first mixture produced by mixing the anthracite and the coal
powder; and
obtaining coal briquettes by forming the first mixture,
wherein the first mixture includes anthracite at over 0 wt% to 30 wt%
and the balance of coal powder.
10. The method of claim 9, wherein
37
the preparing of a first mixture produced by mixing the anthracite and
the coal powder and the obtaining of coal briquettes by forming the first mixture
includes
preparing a first mixture produced by mixing the anthracite and the coal
powder, manufacturing a second mixture produced by mixing a hardener, a
binder, or a combination thereof with the first mixture, and obtaining coal
briquettes by forming the second mixture.
11. The method of claim 10, wherein
the hardener includes 1 to 5 parts by weight with respect to the first
mixture of 100 parts by weight.
12. The method of claim 11, wherein
the hardener is one or more substances selected from a group of
quicklime, slaked lime, limestone, calcium carbonate, cement, bentonite, clay,
silica, silicate, dolomite, phosphoric acid, sulfuric acid, and oxides.
13. The method of claim 10, wherein
the binder is included at 5 to 15 parts by weight with respect to the first
mixture of 100 parts by weight.
14. The method of claim 13, wherein
the binder is one or more substances selected from a group of molasses,
bitumen, asphalt, coal tar, pitch, starch, water glass, plastic, polymer resin, and
38
oil.
15. The method of claim 9, wherein
in the obtaining of coal briquettes by forming the first mixture,
the forming is performed by compressing with a roll press.
16. The method of claim 9, wherein
in the preparing of anthracite,
the grain size of the anthracite is over 0 mm and 5 mm or less.
17. The method of claim 9, wherein
the anthracite includes meta-anthracite.
18. The method of claim 9, wherein
a hot strength index of the obtained coal briquettes is 70 % or more.
19. An apparatus for manufacturing the coal briquettes of any one of
claims 1 to 8, comprising:
an anthracite storage that stores anthracite;
an anthracite conveying pipe that is connected to the anthracite storage
and conveys the anthracite to the anthracite storage;
a coal powder storage that stores coal powder;
a binder storage that stores a binder;
a hardener storage that stores a hardener;
39
a mixer that provides a mixture by mixing anthracite from the anthracite
storage, coal powder from the coal powder storage, a binder from the binder
storage, and a hardener from the hardener storage; and
a molding machine that forms a mixture using the mixture provided from
the mixer.
20. The apparatus of claim 19, wherein
the anthracite storage is directly connected with the.