COAL BRIQUETTE AND PRODUCTION METHOD THEREFOR
[Technical Field]
The present invention relates to coal briquettes and a method for
manufacturing the same. More particularly, the present invention relates to
coal briquettes including low-grade coal and a method for manufacturing the
same.
[Background Art]
10 In a smelting reduction iron-making method, a reducing furnace
reducing iron ore and a melter-gasifier melting reduced iron ore are used. In
the case of melting iron ore in the melter-gasifier, as a heat source to meit iron
ore, coal briquettes are charged into the melter-gasifier. Here, reduced iron is
melted in the melter-gasifier, transformed to molten iron and slag, and then
tfi discharged to the outside. The coal briquettes charged into the melter-gasifier
form a coal-packed bed. After oxygen is injected through a tuyere installed at
the melter-gasifier, it combusted the coal-packed bed to generate a combustion
gas. The combustion gas is transformed into hot reducing gas while rising
through the coal-packed bed. The hot reducing gas is discharged outside the
,;o melter-gasifier to be supplied to the reducing furnace as the reducing gas.
The coal briquettes may be prepared by using bituminous coais. A
ratio of the bituminous coafs to the coal is very low, while the bituminous coal is
not produced at afl in Korea. Accordingly, all the bituminous coals required for
1
preparing molten irons is imported from abroad to be used. Most of the
bituminous coals are produced only in a few countries such as Australia,
Canada, and the United States across the world, thereby high-quality
bituminous coal used for iron making is being gradually depleted, so a supply
:i and demand imbalance is caused and prices serioulsy fluctuate.
[DISCLOSURE]
[Technical Problem]
The present invention has been made in an effort to provide A method
for manufacturing coal briquettes including low-grade coals.
10 [Technical Solution]
An exemplary embodiment of the present invention provides a method
for manufacturing coal briquettes charged into a dome part of the meiter-gasifier
to be rapidly heated in an apparatus for manufacturing molten iron including i) a
meiter-gasifier into which reduced irons are charged, and ii) a reducing furnace
ID connected to the meiter-gasifier and providing the reduced iron. The method
includes i) providing fine coal; ii) preparing a mixture by mixing a hardening
agent of 1 to 5 parts by weight and a binder of 5 to 15 parts by weight with
respect to fine coals of 100 parts by weight; and iii) molding the mixture. In the
providing of the fine coal, the fine coals include i) low-grade coal of more than 0
•/{) and 50wt% or less and ii) remaining carbonaceous materials. The low-grade
coal has a volatile matter {on a dry basis) of 25wt% to 40wt% and a free
swelling index of more than 0 and less than 3.
In the providing of the fine coal, a gross calorific value on a dry basis of
2
the fine coals may be 5500 Kcal/kg to 7000 Kcal/kg. In the providing of the
fine coals, a carbon source additive of more than 0 wt% and 20 wt% or less
may be added to the fine coal. The carbon source additive may include at
least one carbon source selected from a group consisting of fine cokes, coke
dusts, graphites, activated carbons, and carbon blacks. An amount of a first
carbon included in the carbon source additive may be greater than that of a
second carbon included in the carbonaceous materials.
In the providing of the fine coals, the amount of the low-grade coals may
be 10wt% to 40wt%. More preferably, the amount of the low-grade coals may
be 15wt% to30wt%.
In the preparing of the mixture, the hardening agent may be at least one
material selected from a group consisting of quicklime, slaked lime, limestone,
calcium carbonate, cement, bentonite, clay, silica, silicate, dolomite, phosphoric
acid, sulfuric acid, and an oxide. In the preparing of the mixture, the binder
may be at least one material selected from a group consisting of molasses,
bitumen, asphalt, coal tar, pitch, starch, water glass, plastic, a polymer resin,
and oil
[Advantageous Effects]
Since the coal briquettes are manufactured by using iow-grade coal,
manufacturing cost of the coal briquettes may be largely decreased. Further, a
scope of resource utilization may be increased by using the low-grade coal.
[Description of the Drawings]
FIG. 1 is a schematic flowchart of a method for manufacturing coal
briquettes according to an exemplary embodiment of the present invention,
3
FIG. 2 is a schematic diagram of an apparatus for manufacturing molten
irons using the coal briquettes manufactured in FIG. 1.
FIG. 3 is a schematic diagram of another manufacturing apparatus of
molten irons using the coal briquettes manufactured in FIG. 1.
) [Mode for Invention]
Terms such as first, second, and third are used to illustrate various
portions, components, regions, layers, and/or sections, but not to limit them.
These terms are used to discriminate the portions, components, regions, layers,
or sections from the other portions, components, regions, layers, or sections.
in Therefore, the first portion, component, region, layer, or section as described
below may be the second portion, component, region, layer, or section within
the scope of the present invention.
It is to be understood that the terminology used therein is only for the
purpose of describing particular embodiments and is not intended to be limiting.
i.) It must be noted that, as used in the specification and the appended claims, the
singular forms include plural references unless the context clearly dictates
otherwise. It will be further understood that the terms "comprises" and/or
"comprising," when used in this specification, specify the presence of stated
properties, regions, integers, steps, operations, elements, and/or components,
•AO but do not preclude the presence or addition of one or more other properties,
regions, integers, steps, operations, elements, and/or components thereof.
Unless it is mentioned otherwise, all terms including technical terms and
scientific terms used herein have the same meaning as the meaning generally
understood by a person with ordinary skill in the art to which the present
4
invention belongs. The terminologies that are defined previously are further
understood to have the meanings that coincide with related technical
documents and the contents that are currently disclosed, but are not to be
interpreted as the ideal or very official meaning unless it is defined otherwise.
) It is understood that the term "hole" used below includes all of
penetrating or digging shapes in dot, line, or face forms. Accordingly, the term
"hole" includes all of shapes formed as a cavity or formed as a channel.
The present invention will be described more fully hereinafter with
reference to the accompanying drawings, in which exemplary embodiments of
10 the invention are illustrated. As those skilled in the art would realize, the
described embodiments may be modified in various different ways, all without
departing from the spirit or scope of the present invention.
FIG. 1 is a schematic flowchart of a method for manufacturing coal
briquettes according to an exemplary embodiment of the present invention. A
!•) flowchart of the manufacturing method of the coal briquettes of FIG. 1 is just to
exemplify the present invention, and the present invention is not limited thereto.
Accordingly, the manufacturing method of the coal briquettes may be variously
modified.
As illustrated in FIG. 1, the manufacturing method of the coal briquettes
-!o includes i) providing fine coals, ii) manufacuring a mixture by mixing a
hardening agent of 1 to 5 parts by weight and a binder of 5 to 15 parts by weight
with respect to the fine coal of 100 parts by weight, and iii) molding the mixture.
In addition, if necessary, the method for manufacturing coal briquettes may
further include other processes.
5
First, in step S10, the fine coals are provided. The fine coals include
low-grade coals and remaining carbonaceous materials- An amount of a
volatile matter included in the fine coal is 20 wt% to 35 wt%. If the amount of
the volatile matter is very little, a sufficient amount of reducing gas required for
.> reducing iron ore may not be manufactured by charging the coai briquettes
manufactured by the fine coals into the melter-gasifier. Further, if the amount
of the volatile matter is very great, the coal briquettes charged into the meltergasifier
are easily differentiated and thus a heat source required for melting
reduced iron charged into the melter-gasifier may not be sufficiently ensured.
i!) Accordingly, the amount of the volatile matter is controlled in the
aforementioned range.
The coal may be classified by various types. In order to classify the
coal, the degree of coalification may be used as a reference. The degree of
coalification means a process in which a volatile matter of a plant is reduced
if) and amount of fixed carbon is increased according to changes in a time,
pressure, and a temperature in the underground. The coal may be classified
as follows according to the degree of coalification. That is, the coal is
classified into peat coal having carbon (on dry ash free basis) of about 60 % or
less, brown coal having carbon of about 60% to 70%, sub-bituminous coal
:>o having carbon of about 70% to 75%, bituminous coal having carbon of about
75% to 85%, and anthracite coal having carbon of about 85% to 94%, according
to the degree of coalification.
Meanwhile, the coals may be classified into coking coal and non-coking
coal according to a coking property. Bituminous coal having a coking property
6
has a characteristic in which coal particles are coupled to each other during
carbonization. The coking property means that coal particles are contracted by
solidification around 450T to 500"C while having heat softening and a flowing
phenomenon around 350*0 to 4001 and being coupled to each other to be
.1 swollen by generation of pyrolysis gas when the coal is heated. The coking
property is evaluated as a free swelling index (FSI) by a measuring method (KS
E ISO 501) for a coal-crucible swelling index in which a swelling property of the
coal is measured by heating the coal up to a final temperature of 820 + 5 °C.
Coal having an FSI of 3 or more is classified as coking coal, and coal having an
si FSI of less than 3 or less is classified as non-coking coal.
Bituminous coal having the coking property is mainly used for iron
making for manufacturing coke. Meanwhile, since the non-coking coal has no
binding capacity between coal particles, coke quality is deteriorated while the
non-coking coal is used for manufacturing coke and thus the non-coking coal is
not used for iron making. Thus, brown coal which is a non-coking coal and has
a high volatile matter content, subbituminous coal, and bituminous coal having
no coking property have been mainly used only for power generation.
Meanwhile, anthracite coal which is a non-coking coal and has high fixed
carbon and calorific value is mainly used in a fine coal injection (PCI) process.
The low-grade coal means inexpensive coal having a high volatile
matter content, as a non-coking coal of which a free swelling index (FSI) is iess
than 3. The low-grade coal is mainly pulverized to fine coal to be used for
power generation. In an exemplary embodiment of the present invention,
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inexpensive low-grade coal which is not used as coal for metallurgy is used.
The coal briquettes charged into the melter-gasifier directly contact a hot
gas flow at approximately 1000"C at a dome part of the melter-gasifier to be
rapidly heated at 30°C/min or more. When a heating speed increases, a
) softening zone is increased to a high temperature and fluidity rapidly increases.
Ultimately, non-coking coals which are not melted at a low heating speed of 3
°C/min are also melted at a rapid heating speed. When a change in viscosity
for a temperature of the coals is large, tar particles are large, and the heating
speed is fast, fluidity is changed according to discharge of tar, lots of oxygen
) exists, and cross-bonding is easily generated at a low heating speed. As a
result, the fluidity of the coals is increased by rapid heating. Therefore, even
when melting is not easy, soften-melting is generated by rapid heating.
Since the coke for iron making is manufactured by heating at a low
speed of 3"C/min, high-quality coke may be manufactured if the fluidity of the
) coal itself is high. Accordingly, if inexpensive low-grade coal having a low
coking property and low fluidity is used, quality of the coke deteriorates. On
the contrary, the coal briquettes are rapidly heated at 30°C/min or more by
directly contacting a hot gas flow at approximately 1000°C at the dome part of
the melter-gasifier. Accordingly, the coal briquettes may be manufactured with
) the inexpensive low-grade coal which cannot be used when the coke for iron
making is manufactured. For example, coal for power generation may be used
as the low-grade coal.
The fine coal forming the coal briquettes charged into the melter-gasifier
8
influences the behavior of the melter-gasifier. Accordingly, only the fine coal
having limited characteristics may be used in the melter-gasifier. Here, the fine
coal need to satisfy various conditions in terms of cold strength, hot strength, a
hot differentiation rate, a coal ash content, and a fixed carbon content.
i Meanwhile, high-quality coal may be manufactured by mixing coal for controlling
quality having a high mean reflectance with fine coal, but there is a problem in
that manufacturing cost of the coai briquettes increases.
The amount of low-grade coal may be 0 to 50wt%. When the amount
of low-grade coal is very large, since the quality of the manufactured coal
i!) briquettes deteriorates, the coal briquettes are differentiated well at a high
temperature and the strength of char of the coal briquettes deteriorates, and
thereby the operation of the melter-gasifier may be unstabilized. Accordingly,
the amount of low-grade coal is controlled to the aforementione range.
Preferably, the amount of low-grade coal may be 10wt% to 40wt%. More
\:> preferably, the amount of low-grade coal may be 15wt% to 30wt%.
A gross calorific value on dry basis of low-grade coals may be
5500Kcal/kg to 7000Kcal/kg. The calorific value represents a calorific value
discharged by coal per unit mass during perfect combustion. The calorific
value is measured by a KS E3707 standard and is represented by the gross
•>o calorific value on a dry basis. Strong coking coal having a high coking property
among bituminous coal mainly used for metallurgy has a high calorific value of
approximately 7500 Kcal/kg or more, and weak coking coals have a calorific
value of 7000 Kcal/kg to 7500 Kcal/kg. Metallurgical coal has a high calorific
value of approximately 7000 Kcal/kg or more, but the low-grade coal has
9
volatile matter of 25wt% to 40wt%, an FSI (on a dry basis) of more than 0 and
less than 3, and a low calorific value of 5500 Kcal/kg to 7000 Kcal/kg.
When the volatile matter content of low-grade coal is very high, the
volatile matter component included in the coal briquettes is rapidly discharged
:> and thus the coal briquettes are differentiated when the coal briquettes are
charged into the melter-gasifier. As a result, the operation of the meltergasifier
may become unstable. Among the coal having the volatile matter
content of less than 25%, the coking coal having a high FSI is expensive highgrad
coal which is mainly used for manufacturing cokes in an iron making
io process. On the contrary, non-coking coal having a low FSI is coal having a
high calorific value such as anthracite coals which is mainly used in a process
of injecting pulverized fine coals. Accordingly, there is no coal having a volatile
matter content of less than 25%, low FSI, and low calorific value among the lowgrade
coal.
i.) Coal having the high FSI is usable for manufacturing coke and thus is
traded at an expensive price. If coal having a high FSI is used for power
generation, coal is swollen in a proportion to an increase of temperature to
block an injection nozzle during the fine coal injection. Accordingly, only noncoking
coal having an FSI of more than 0 and less than 3 enough to not block
•{() the injection nozzle while charging it may be used for power generation or in the
process of charging fine coal.
When the calorific value of low-grade coal is very low, a sufficient
calorific value for melting reduced iron may not be ensured while the coal
briquettes are charged into the melter-gasifier. Further, low-grade coal having
10
a high calorific value may be used, but non-coking coal having a high calorific
value has a low volatile matter content such as anthracite coal which is mainly
used in the process of injecting fine coal. Accordingly, there is no coal with the
volatile matter content (on a dry basis) of 25% to 40% and high calorific value
.) as non-coking coal having a low FSI, among the low-grade coal. Therefore,
the calorific value of low-grade coal is maintianed in the aforementioned range.
Meanwhile, in the fine coal, a carbon source additive of more than 0
wt% and 20wt% or less may be added. As the carbon source additive, fine
coke, coke dust, graphite, activated carbon, carbon black, or the like may be
10 used. Here, an amount of a first carbon included in the carbon source additive
may be greater than that of a second carbon included in carbonaceous
materials. Accordingly, an amount of fixed carbon of the coal briquettes may
be increased by the carbon source additive.
That is, since the low-grade coal has a high volatile matter content and a
i.) lower content of fixed carbon than that of bituminous coals, the low-grade coal
may not be used for manufacturing molten iron. In the case of using coal
briquettes including the low-grade coal in the melter-gasifier, the amount of
reducing gas generated by coal briquettes is large, but a char production
amount is relatively small. In this case, in order to supply a sufficient amount
:s) the apparatus for manufacturing molten iron 200 in FIG. 3 may be modified in
various shapes. Since the structure of the apparatus for manufacturing molten
iron 200 in FIG. 3 is similar to the structure of the apparatus for manufacturing
molten iron 100 in FIG. 2, [ike reference numerals are used for like parts, and
the detailed description thereof is omitted.
14
As illustrated in FIG. 3, the apparatus for manufacturing molten iron 200
includes a meiter-gasifier 10, a reducing furnace 22, a device for manufacturing
compacted irons 40, and a compacted iron storage bin 50. Here, the
compacted iron storage bin 50 may be omitted.
The manufactured coal briquettes are charged into the melter-gasifier 10.
Here, the coal briquettes generate a reducing gas in the meiter-gasifier 10 and
the generated reducing gas is supplied to a fiuidized-bed reducing furnace.
Fine iron ore is supplied to a plurality of fluidized-bed reducing furnaces 22, and
is manufactured into reduced iron while flowing by reducing gas supplied to the
reducing furnaces 22 from the melter-gasifier 10. The reduced iron is
compacted by the device for manufacturing compacted irons 40 and stored in
the compacted iron storage bin 50. The compacted reduced iron is supplied
from the compacted iron storage bin 50 to the melter-gasifier 10 to be melted in
the melter-gasifier 10. Since the coal briquettes are supplied to the meitergasifier
10 to be transformed to char having permeability, a large amount of gas
generated below the melter-gasifier 10 and the compacted reduced iron more
easily and uniformly pass through the coal-packed bed in the melter-gasifier 10
to manufacture high-quality molten iron.
in the following, the present invention will be described in more detail
through experimental examples. The following experimental examples are just
to exemplify the present invention, and the present invention is not limited
thereto.
Experimental Example
Fine coal having an average shape and a mean grain size of 3.4 mm or
15
less was prepared. The fine coal was manufactured by mixing metallurgical
coal and low-grade coal. A carbon source additive was additionally mixed in
the fine coal. Characteristics of the used metallurgical coal, low-grade coal,
and carbon source additive are listed in the following Table 1. The volatile
matter content of low-grade coal D and low-grade coal E was 30 % or more,
respectively and a coking property (FSI) was 1.
(Table 1)
2.7 parts by weigf
parts by weight of the manufactured fine coals was mixed, and then 10 parts by
io weight of molasses as a binder were uniformly mixed to manufacture a mixture.
The mixture was compacted by a roll press to manufacture coal briquettes of a
pillow shape and having dimensions of 64.5 mm x 25.4 mm x 19.1 mm. The
16
hot strength of the coal briquettes was then measured.
Comparative Example
For comparison with the aforementioned experimental example, the fine
coal was manufactured by using the metallurgical coal and the carbon source
additive without using the low-grade coal. The rest of the manufacturing
processes of the coal briquettes were the same as those in the aforementioend
experimental example.
Experimental Example 1
Fine coal was manufactured by mixing metallurgical coat A of 35wt%,
metallurgical coal B of 25wt%, low-grade coal E of 30wt%, and a carbon source
additive of 10wt%.
Experimental Example 2
Fine coal was manufactured by mixing metallurgical coal A of 35wt%,
metallurgical coal B of 20wt%, low-grade coal E of 30 wt%, and a carbon source
additive of 15wt%.
Experimental Example 3
Fine coal was manufactured by mixing metallurgical coai A of 60wt%,
low-grade coal D of 30wt%, and a carbon source additive of 10wt%.
Experimental Example 4
Fine coal was manufactured by mixing metallurgical coal A of 40wt%,
low-grade coai D of 50wt%, and a carbon source additive of 10wt%.
Experimental Example 5
Fine coal was manufactured by mixing metallurgical coal A of 40wt%,
metallurgical coal B of 30wt%, and low-grade coal D of 30wt%.
17
Experimental Example 6
Fine coal was manufactured by mixing metallurgical coal A of 20wt%,
low-grade coal D of 70wt%, and a carbon source additive of 10wt%.
Experimental Example 7
;i Fine coal was manufactured by mixing metallurgical coal C of 20wt%,
low-grade coal D of 70wt%, and a carbon source additive of 10wt%.
Comparative Example 1
Fine coal was manufactured by mixing metallurgical coal A of 35wt%,
metallurgical coal B of 25wt%, metallurgical coal C of 30wt%, and a carbon
IO source additive of 10wt%.
Experimental Result
The hot strength, the char strength, and the fixed carbon of the coal
briquettes manufactured by Experimental Examples 1 to 7 and Comparative
Example 1 were measured.
i > Hot strength measurement experiment
The hot strength of coal briquettes was measured in order to determine
the differentiation degree of the coal briquettes generated in the melter-gasifier.
To this end, under a heating condition set as 1000*0 and an inert nitrogen
atmosphere, coal briquettes of approximately 1Kg were injected into a
;-!() cylindrical reaction furnace with a diameter of 280mm at room temperature, and
then the cylindrical reaction furnace was rotated at a rotational speed of 2rpm
for 15minutes. In addition, the cylindrical reaction furnace was additionally
rotated at a rotational speed of 20rpm for 30minutes to manufacture coal
briquette char. As the differentiation degree of the coal briquette char was
18
decreased, it was determined that the hot strength is excellent, and thus the hot
strength was measured at a ratio of char with a grain size of 10mm or more as a
contrast ratio.
Char strength measurement experiment
in order to verify whether the strength of char manufactured in a
measuring apparatus of the hot strength of the coal briquettes deteriorates or
not, the strength of the coal briquette char was evaluated by using an l-type
drum device for measuring hot strength of coke for metallurgy. That is, 200g of
coal briquette char with a grain size of 16 mm or more was put in the l-type
drum device having a length of 600mm for measuring the hot strength of coke
and rotated 600 at a speed of 20 rotations per minute, and then a residual ratio
of 100mm or more was measured, and as a result, abrasion and impact
resistance of the coal briquette char were measured. As a contrast ratio of the
coal briquette char obtained by the hot strength measurement method is larger
and the coal briquette char strength is higher, the differentiation of the coal
briquettes in the melter-gasifier is small, thereby ensuring the char strength at a
high temperature. The measurement results of the aforementioned hot
strength and char strength and the measured amount of fixed carbon are listed
in the following Table 2.
(Table 2)
As listed in Table 2, the hot strength, the char strength, and fixed carbon
of coal briquettes according to Experimental Example 1 to Experimental
Example 5 were similar to the hot strength, the char strength, and fixed carbon
of coal briquettes according to Comparative Example 1. Accordingly, even
20
though fine coal is manufactured by mixing low-grade coal, coal briquettes
having the same characteristics as the coal briquettes without the low-grade
coals may be manufactured. However, like Experimental Example 6 and
Experimental Example 7, when coal briquettes are manufactured by using a
) large amount of low-grade coals, the char stength was lower than the char
stength of the coal briquettes manufactured according to Experimental Example
1 to Experimental Example 5 and the hot strength deteriorated, and as a result,
it was not suitable for being used as the coai briquettes. Therefore, when a
certain amount of low-grade coals was mixed, it could be seen that
J manufacturing costs of coal briquettes were reduced and the charactenstics of
coal briquettes were maintained.

[CLAIMS]
[Claim 1]
A method for manufacturing coal briquettes charged into a dome part of
the melter-gasifier to be rapidly heated in an apparatus for manufacturing
molten iron comprising:
a melter-gasifier into which reduced irons are charged, and a reducing
furnace connected to the melter-gasifier and providing the reduced iron, the
method comprising;
providing fine coal;
preparing a mixture by mixing a hardening agent of 1 to 5 parts by
weight and a binder of 5 to 15 parts by weight with respect to fine coals of 100
parts by weight; and
molding the mixture, and
wherein in the providing of the fine coal, the fine coals comprise lowgrade
coal of more than 0 and 50wt% or less and remaining carbonaceous
materials, and the low-grade coal has a volatile matter (on a dry basis) of
25wt% to 40wt% and a free swelling index of more than 0 and less than 3.
[Claim 2]
The method of claim 1, wherein in the providing of the fine coal, a gross
calorific value on a dry basis of the fine coals is 5500 Kcal/kg to 7000 Kcal/kg.
[Claim 3]
22
The method of claim 1, wherein in the providing of the fine coals, a
carbon source additive of more than 0 wt% and 20 wt% or less is added to the
fine coal.
[Claim 4]
The method of claim 3, wherein the carbon source additive comprises at
least one carbon source selected from a group consisting of fine cokes, coke
dusts, graphites, activated carbons, and carbon blacks, and an amount of a first
carbon included in the carbon source additive is greater than that of a second
IO carbon included in the carbonaceous materials.
[Claim 5]
The method of ciaim 1, wherein in the providing of the fine coals, the
amount of the low-grade coals are 10wt% to 40wt%.
[Claim 6]
The method of claim 5, wherein the amount of the low-grade coals are
15wt% to 30wt%.
•>.u [Claim 7]
The method of claim 1, wherein in the preparing of the mixture, the
hardening agent is at least one material selected from a group consisting of
quicklime, slaked lime, limestone, calcium carbonate, cement, bentonite, clay,
23
silica, silicate, dolomite, phosphoric acid, sulfuric acid, and an oxide.
[Claim 8]
The method of claim 1, wherein in the preparing of the mixture, the
,> binder is at least one material selected from a group consisting of molasses,
bitumen, asphalt, coal tar, pitch, starch, water glass, plastic, a polymer resin,