TECHNICAL FIELD
The present invention relates to a method for preparing
blast furnace injection coal, blast furnace injection coal, and
a method for using the blast furnace injection coal.
5 BACKGROUND ART
Blast furnace installations have been configured to be
capable of producing pig iron from iron ore by charging starting
materials such as iron ore, limestone, and coke through the top
of the blast furnace main body into the interior, and injecting
10 hot air and blast furnace injection coal (pulverized coal) as
an auxiliary fuel through a tuyere on a lower side of a side
portion of the blast furnace main body.
To stably operate the above-described blast furnace
installation, the blast furnace injection coal is required to
15 be such that the accretion of ash of the blast furnace injection
coal or the occlusion by ash of the blast furnace injection coal
should be suppressed in a pathway leading to the tuyere of the
blast furnace main body.
For example, it has been proposed to improve the
20 combustibility of blast furnace injection coal by measuring the
softening points of ash in pulverized coals in advance, adding
a CaO-based flux such as limestone or serpentinite or another
pulverized coal to each of the pulverized coals having softening
points of ash of lower than 1300°C in a necessary amount
25 determined based on the softening point of the pulverized coal
to adjust the softening point of the ash in the pulverized coal
to 1300°C or higher, and, subsequently, injecting only the
pulverized coals whose softening points of ash are 1300°C or
higher into the interior through a tuyere of a blast furnace
30 main body (for example, see Patent Document 1 below).
3
Furthermore, a blast furnace operation method has been
proposed, wherein, for example, any one or two or more of
CaO-based, MgO-based, and SiO2-based fluxes are injected into
the interior of a blast furnace through a tuyere (for example,
5 see Patent Document 2 below).
PRIOR ART DOCUMENT
PATENT DOCUMENT
Patent Document 1: Japanese Unexamined Patent Application
10 Publication No. H5-156330A
Patent Document 2: Japanese Unexamined Patent Application
Publication No. H3-291313A
SUMMARY OF THE INVENTION
15 PROBLEMS TO BE SOLVED BY THE INVENTION
However, in the technique described in Patent Document
1, calcium oxide added as the flux has large particle diameters
(fine calcium oxide particles have diameters of about 10 μm),
and it takes a long time to uniformly mix the calcium oxide with
20 the slag in the blast furnace. Hence, there is a possibility
that the effect of the addition of the flux to elevate the
softening point of the blast furnace injection coal tends to
be difficult to obtain, also when a large amount of blast furnace
injection coal is injected.
25 In Patent Document 2, described is only a blast furnace
operation method which assures fluidity of bosh slag produced
in the blast furnace by setting the viscosity at 1450°C to 10
poise or lower. Therefore, there is a possibility that the
accretion of ash of the blast furnace injection coal or the
30 occlusion by ash of the blast furnace injection coal in a pathway
4
leading to the tuyere of the blast furnace main body cannot be
suppressed.
From such facts, the present invention has been made to
solve the problems described above, and an object of the present
invention is to provide a method for preparing blast 5 furnace
injection coal which makes it possible to obtain blast furnace
injection coal which is resistant to fluidity failure of slag
in the blast furnace main body, even when the amount of the coal
injected into the blast furnace main body is increased, as well
10 as blast furnace injection coal and a method for using the blast
furnace injection coal.
MEANS FOR SOLVING THE PROBLEMS
A method for preparing blast furnace injection coal
pertaining to a first aspect of the invention which solves the
15 above problems comprises: a first step of analyzing ash of
run-of-mine coal and weight percentages of Al, Si, Ca, and Mg
in the ash; a second step of deriving an ash melting point of
the coal based on data obtained by the analysis; a third step
of selecting a metal species to be supported on the coal and
20 deriving the amount of the metal species to be supported based
on data obtained in the first step and the second step to adjust
the melting point of the ash of the coal to 1200 to 1400°C; a
fourth step of supporting the metal in the amount to be supported
onto the coal by an ion exchange method; and a fifth step of
25 pyrolyzing the coal obtained in the fourth step.
A method for preparing blast furnace injection coal
pertaining to a second aspect of the invention which solves the
above problems is the method for preparing blast furnace
injection coal pertaining to the above-described first aspect
30 of the invention, wherein the metal is at least one of calcium
5
and magnesium.
A method for preparing blast furnace injection coal
pertaining to a third aspect of the invention which solves the
above problems is the method for preparing blast furnace
injection coal pertaining to the above-described first 5 or
second aspect of the invention, wherein the coal is thermally
treated at 350 to 550°C in the fifth step to adjust a residual
volatile content to 15 to 35%.
A method for preparing blast furnace injection coal
10 pertaining to a fourth aspect of the invention which solves the
above problems is the method for preparing blast furnace
injection coal pertaining to any one of the above-described
first to third aspects of the invention, wherein the amount of
the metal to be supported on the coal is 0.2 to 1.55 in terms
15 of (CaO+MgO)/SiO2 weight ratio.
A method for preparing blast furnace injection coal
pertaining to a fifth aspect of the invention which solves the
above problems is the method for preparing blast furnace
injection coal pertaining to the above-described fourth aspect
20 of the invention, wherein the amount of the metal to be supported
on the coal is 0.25 to 1.4 in terms of (CaO+MgO)/SiO2 weight
ratio.
A method for preparing blast furnace injection coal
pertaining to a sixth aspect of the invention which solves the
25 above problems is the method for preparing blast furnace
injection coal pertaining to the above-described fifth aspect
of the invention, wherein the amount of the metal to be supported
on the coal is 0.35 to 1 in terms of (CaO+MgO)/SiO2 weight ratio.
Blast furnace injection coal pertaining to a seventh
30 aspect of the invention which solves the above problems is
6
obtained by the method for preparing blast furnace injection
coal pertaining to any one of the above-described first to sixth
aspects of the invention.
A method for using blast furnace injection coal
pertaining to an eighth aspect of the invention which 5 solves
the above problems comprises injecting blast furnace injection
coal obtained by the method for preparing blast furnace
injection coal pertaining to any one of the above-described
first to sixth aspects of the invention through a tuyere into
10 an interior of a blast furnace main body of a blast furnace
installation.
EFFECT OF THE INVENTION
According to the present invention, the metal supported
on the coal is in the form of nanoparticles and is uniformly
15 dispersed in the coal, and the uniform mixing of the combustion
ash, the metal in the form of the nanoparticles, and the slag
in the blast furnace main body together is accelerated. Hence,
it is possible to obtain blast furnace injection coal which is
resistant to fluidity failure of slag in the blast furnace main
20 body, even when the amount of the coal injected into the blast
furnace main body is increased.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a flowchart illustrating a procedure of a method
for preparing blast furnace injection coal pertaining to an
25 embodiment of the present invention.
Fig. 2 is a quaternary phase diagram for SiO2-CaO-MgO-20%
Al2O3, where the total weight of Al, Si, Ca, and Mg oxides in
the ash of coal used in the method for preparing blast furnace
injection coal pertaining to an embodiment of the present
7
invention is taken as 100% by weight, and the Al2O3 content is
taken as 20% by weight.
Fig. 3 is a graph which illustrates the relationship
between the (CaO+MgO)/SiO2 weight ratio and the ash melting
point and which is used in the method for preparing blast 5 t furnace
injection coal pertaining to an embodiment of the present
invention.
MODE FOR CARRYING OUT THE INVENTION
Embodiments of a method for preparing blast furnace
10 injection coal, blast furnace injection coal, and a method for
using the blast furnace injection coal pertaining to the present
invention will be described based on the drawings, but the
present invention is not limited only to the following
embodiments described based on the drawings.
15 An embodiment of the method for preparing blast furnace
injection coal, the blast furnace injection coal, and the method
for using the blast furnace injection coal pertaining to the
present invention will be described based on Figs. 1 to 3.
The blast furnace injection coal pertaining to this
20 embodiment is blast furnace injection coal to be injected
through a tuyere into an interior of a blast furnace main body
of a blast furnace installation, and, as shown in Fig. 1, can
be easily prepared as follows. Specifically, ash of
run-of-mine coal is analyzed, and the weight percentages of Al,
25 Si, Ca, and Mg in the ash of the coal is analyzed (first step
S1); an ash melting point of the coal is derived based on data
obtained by the analysis (second step S2); a metal species to
be supported on the coal is selected and the amount of the metal
to be supported on the coal is derived based on the derived ash
30 melting point of the coal (third step S3); the metal in the amount
8
to be supported is supported based on data obtained in the third
step S3 onto the coal by an ion exchange method (fourth step
S4); and the coal supporting the metal (hereinafter, referred
to as metal-supporting coal) is pyrolyzed (fifth step S5).
In the first step S1, the composition of the ash 5 of
run-of-mine coal is the data most basically used as the quality
of coal (run-of-mine coal), and it is possible to use the data
obtained by, for example, the industrial analysis set forth in
JIS M 8812 (2004) implemented when the run-of-mine coal is
10 produced or used.
In the first step S1, the weight percentages of Al, Si,
Ca, and Ma in the ash of coal are the data most basically used
as the quality of coal (run-of-mine coal), and it is possible
to use the data obtained by, for example, the method for
15 analyzing metals in exhaust gas (a method based on ICP
(high-frequency inductively coupled plasma)) set forth in JIS
K 0083, or the method for analyzing the coal ash and the coke
ash set forth in JIS M 8815 implemented when the run-of-mine
coal is produced or used.
20 It is preferable to use, for example, a low-grade coal
(oxygen atom content (dry base): higher than 18% by weight;
average pore diameter: 3 to 4 nm) generally having many carboxy
groups (-COOH) and hydroxy groups (-OH) such as lignite or
sub-bituminous coal as the coal (run-of-mine coal) analyzed in
25 the first step S1.
In the second step S2, the ash melting point of the coal
can be derived, based on the data obtained in the first step
S1 (the weight percentages of Al, Si, Ca, and Mg in the ash of
the coal), by taking the Al, Si, Ca, and Mg oxides in the ash
30 as 100% by weight, converting the Al2O3 content to 20% by weight,
9
and using, for example, a quaternary phase diagram for
SiO2-CaO-MgO-20% Al2O3 shown in Fig. 2.
In the third step S3, the metal species to be supported
on the coal is preferably selected based on the data obtained
in the first step S1 (the weight percentages of SiO2, CaO, 5 and
MgO, where the Al, Si, Ca, and Mg oxides in the ash is taken
as 100% by weight, and the Al2O3 content is converted to 20%
by weight) and the data obtained in the second step S2 (the ash
melting point of the coal).
10 As the species of metal (metal species), it is preferable
to select, for example, at least one of alkaline earth metals
such as magnesium (Mg) and calcium (Ca). Especially when the
silicon (Si) content in the ash of the coal is high (the weight
percentage of SiO2 is, for example, 75% by weight or higher),
15 and the melting point of the ash is high (for example, 1500°C
or higher), it is preferable to support calcium (Ca) on the coal.
In the third step S3, the supported amount of the metal
to be supported on the coal is preferably derived based on the
data obtained in the first step (the weight percentages of SiO2,
20 CaO, and MgO, where the Al, Si, Ca, and Mg oxides in the ash
is taken as 100% by weight, and the Al2O3 content is converted
to 20% by weight, as well as the ash melting point of the coal),
and the metal selected in the third step S3.
In the fourth step S4, the metal-supporting coal can be
25 obtained by, for example, immersing the coal in an aqueous
alkaline solution of the metal (for example, Ca(OH)2, Mg(OH)2,
or the like) for a certain period (for example, 1 hour to 8 hours),
followed by dehydration.
In the fifth step S5, the metal-supporting coal is
30 preferably thermally treated in a thermal treatment furnace
10
such as a kiln at, for example, 350 to 550°C for, for example,
30 minutes to 2 hours to adjust a residual volatile content
to 15 to 35%. This results in formation of nanoparticles
(several ten nanometers to several hundred nanometers) of the
metal, so that the metal is uniformly dispersed in the 5 obtained
blast furnace injection coal.
The blast furnace injection coal produced by the method
for preparing blast furnace injection coal pertaining to this
embodiment is obtained by supporting the metal on the coal by
10 an ion exchange method and pyrolyzing the coal supporting the
metal to adjust the ash melting point of the coal to lower than
1400°C with the Al, Si, Ca, and Mg oxides in the ash of the coal
being taken as 100% by weight, and the Al2O3 content in the ash
being taken as 20% by weight. Hence, the metal supported on
15 the coal is converted into nanoparticles, and uniformly
dispersed in the coal. This accelerates the uniform mixing of
the combustion ash, the metal in the form of the nanoparticles,
and the slag in the blast furnace main body together. Therefore,
it is possible to obtain blast furnace injection coal which is
20 resistant to fluidity failure of the slag in the blast furnace
main body, even when the amount of the coal injected into the
blast furnace main body is increased. This makes it possible
to reduce the amount of coke used.
Moreover, the metal in the form of the nanoparticles
25 exerts a catalytic action, and can promote the combustion and
gasification reactions in the presence of oxygen even at low
temperature.
The ash of the coal and the metal are dispersed in the
coal, and the mixing of the metal in the form of the nanoparticles,
30 the combustion ash, and the slag is started after the coal is
11
combusted. Hence, by converting the metal into the form of the
nanoparticles before the coal is injected into the tuyere of
the blast furnace main body, the combustion starts and ends
earlier, and the mixing is started earlier, so that the speed
of the uniform mixing 5 increases.
Since the coal is pyrolyzed before being injected into
the tuyere of the blast furnace main body, heat for thermal
decomposition is unnecessary, and the amount of generated
inactive thermal decomposition gas decreases. Hence, the
10 combustion temperature increases, and the combustion speed
increases, so that the combustion is completed earlier, and the
mixing is started earlier.
In other words, by pyrolyzing the coal before being
injected into the tuyere of the blast furnace main body,
15 properties of the coal are changed and the metal is converted
into nanoparticles. Consequently, the combustion is
accelerated, so that the metal in the form of the nanoparticles,
the combusted coal, and the slag are mixed together earlier,
and the uniform mixing thereof is accelerated. This results
20 in increase in fluidity of the mixture slag, and the
dischargeability is improved.
Since the flux is injected in Patent Document 2 mentioned
above, it is necessary to provide each blast furnace with a
storage tank and an injection nozzle for the flux, so that the
25 apparatus is complicated according to the number of the blast
furnaces. However, since desired blast furnace injection coal
can be obtained in this embodiment, the apparatus is not
complicated, and the reliability of operations of the blast
furnace can be increased.
30 Note that, when calcium is supported on the coal, the total
12
weight percentage of calcium oxide (CaO) and magnesium oxide
(MgO) relative to the weight percentage of silica (SiO2) is
preferably 0.2 (=0.14/0.66) or higher and 1.55 (=0.486/0.314)
or lower, more preferably 0.25 (=0.16/0.64) or higher and 1.4
(=0.47/0.33) or lower, and further preferably 5 bly 0.35
(=0.208/0.592) or higher and 1 (=0.4/0.4) or lower, where the
total weight of Al, Si, Ca, and Mg oxides in the ash of the coal
is taken as 100% by weight, and the Al2O3 content is converted
to 20% by weight. In other words, calcium oxide is preferably
10 supported on the coal with the total weight percentage of
calcium oxide (CaO) and magnesium oxide (MgO) being 14% by
weight to 48% by weight, calcium oxide is more preferably
supported on the coal with the total weight percentage of
calcium oxide (CaO) and magnesium oxide (MgO) being 16% by
15 weight to 47% by weight, and calcium oxide is further preferably
supported on the coal with the total weight percentage of
calcium oxide (CaO) and magnesium oxide (MgO) being 21% by
weight to 40% by weight. This is because various kinds of coal
for which the composition of the ash and the ash melting point
20 have been already known can be summarized as shown by black
circles in Fig. 3, when attention is focused on the weight ratio
of calcium oxide and magnesium oxide to silica and the ash
melting point, and the approximate line of these data is as shown
by the curve L1 in Fig. 3. In other words, as shown in Fig.
25 3, a (CaO+MgO)/SiO2 ratio of lower than 0.2 or higher than 1.55
is not preferable, because the ash melting point of the blast
furnace injection coal becomes higher than 1400°C, a
(CaO+MgO)/SiO2 ratio of lower than 0.25 or higher than 1.4 is
not preferable, because the ash melting point of the blast
30 furnace injection coal becomes higher than 1300°C, and a
13
(CaO+MgO)/SiO2 ratio of lower than 0.35 or higher than 1 is not
preferable, because the ash melting point of the blast furnace
injection coal becomes higher than 1200°C.
[Other Embodiments]
Hereinabove, the method for preparing blast fur5 nace
injection coal in which an alkaline earth metal such as Mg or
Ca is supported on the coal by an ion exchange method; however,
it is also possible to employ a method for preparing blast
furnace injection coal in which an alkaline earth metal such
10 as beryllium (Be) is supported as the metal on the coal. Such
a method for preparing blast furnace injection coal also
achieves the same operations and effect as those of the method
for preparing blast furnace injection coal pertaining to the
above-described embodiment.
15 It is also possible to employ a method for preparing blast
furnace injection coal in which a boron-group element such as
aluminum (Al) is supported on the coal. Such a method for
preparing blast furnace injection coal also achieves the same
operations and effect as those of the method for preparing blast
20 furnace injection coal pertaining to the above-described
embodiment.
It is also possible to employ a method for preparing blast
furnace injection coal in which an alkali metal such as Li, Na,
or K is supported on the coal. Such a method for preparing blast
25 furnace injection coal also achieves the same operations and
effect as those of the method for preparing blast furnace
injection coal pertaining to the above-described embodiment.
Examples
Working examples performed to confirm the operation and
30 effect of the method for preparing blast furnace injection coal
14
pertaining to the present invention will be described below,
but the present invention is not limited to only the following
working examples described based on various data.
First, as illustrated in Fig. 1, the moisture content of
the coal of a coal type A in the run-of-mine coal state and 5 the
ash of the coal are analyzed, and the weight percentages of Al,
Si, Ca, and Mg in the ash of the coal are analyzed in advance
(first step S1).
[Table 1]
Coal
type
A
Unit
Composition
of ash
SiO2 wt% 57.8
Al2O3 wt% 14.9
TiO2 wt% 0.84
Fe2O3 wt% 17.9
CaO wt% 1.71
MgO wt% 0.8
Na2O wt% 0.39
K2O wt% 2.25
SO3 wt% 1.76
P2O3 wt% 0.1
Total of SiO2, Al2O3, CaO, and MgO wt% 75.21
SiO2 (converted with SiO2, Al2O3, CaO,
and MgO taken as 100 wt%)
wt% 76.9
Al2O3 (converted with SiO2, Al2O3,
CaO, and MgO taken as 100 wt%)
wt% 19.8
CaO (converted with SiO2, Al2O3, CaO,
and MgO taken as 100 wt%)
wt% 2.3
15
MgO (converted with SiO2, Al2O3, CaO,
and MgO taken as 100 wt%)
wt% 1.1
SiO2 (converted with SiO2, CaO, and
MgO taken as 80 wt%)
wt% 76.6
CaO (converted with SiO2, CaO, and
MgO taken as 80 wt%)
wt% 2.3
MgO (converted with SiO2, CaO, and
MgO taken as 80 wt%)
wt% 1.1
In the coal type A described above, the contents of the
oxides of Si, Ca, and Mg in the ash of the coal type A are values
shown in Table 1 above, where the total weight of Al, Si, Ca,
and Mg oxides in the ash of the coal type A is taken as 100%
by weight, and the Al2O3 content is converted to 20% by weight5 .
Accordingly, the ash melting point of the coal type A is located
at the coal type A in Fig. 2, which is a quaternary phase diagram
for SiO2-CaO-MgO-20% Al2O3, where the Al, Si, Ca, and Mg oxides
in ash of coal is taken as 100% by weight, and the Al2O3 content
10 is converted to 20% by weight.
Subsequently, the ash melting point of the coal type A
is determined by using, for example, Fig. 2 based on the CaO
content, the MgO content, and the SiO2 content in the ash, where
the total weight of Al, Si, Ca, and Mg oxides in the ash of the
15 coal type A is taken as 100% by weight, and the Al2O3 content
is converted to 20% by weight.
Subsequently, a metal species to be supported on the coal
type A is selected and the amount of the selected metal to be
supported on the coal type A is derived based on the ash melting
20 point of the coal type A and the region where the ash melting
point of coal is lower than 1400. Here, it can be seen that
the ash melting point of the coal can be 1400°C or lower, when
16
CaO at a ratio of approximately 10% by weight is supported on
the coal type A. Hence, CaO is selected as the metal species
to be supported on the coal type A, and 10% by weight is derived
as the amount of the metal species to be supported.
Subsequently, the CaO is supported on the coal type A 5 by
an ion exchange method, followed by pyrolysis. Thus, blast
furnace injection coal having an ash melting point of 1400°C
or lower can be obtained.
Accordingly, these working examples reveal the following
10 fact. Specifically, when the ash of run-of-mine coal is
analyzed and the weight percentages of Al, Si, Ca, and Mg in
the ash of the coal are analyzed, the ash melting point of the
coal is derived based on data obtained by the analysis, CaO
(metal species) to be supported on the coal is selected and the
15 amount thereof to be supported is derived based on the obtained
data to adjust the ash melting point of the coal to 1200 to 1400°C,
and the metal in the amount to be supported is supported on the
coal by an ion exchange method, followed by pyrolysis, the metal
supported on the coal is converted to nanoparticles and
20 uniformly dispersed in the coal, and the uniform mixing of the
combustion ash, the metal in the form of the nanoparticles,
and the slag in the blast furnace main body is accelerated, and,
hence, it is possible to obtain blast furnace injection coal
which is resistant to fluidity failure of slag in a blast furnace
25 main body, even when the amount of the coal injected into the
blast furnace main body is increased.
INDUSTRIAL APPLICABILITY
The present invention makes it possible to obtain blast
furnace injection coal which is resistant to fluidity failure
30 of slag in a blast furnace main body, even when the amount of
17
the coal injected into the blast furnace main body is increased.
Hence, the present invention can be extremely advantageously
used in iron manufacturing industries.
EXPLANATION OF REFERENCE NUMERALS
L1 approximate line obtained from data (5 line showing
relationship between (CaO+MgO)/SiO2 and ash melting point of
blast furnace injection coal)
S1 first step (analysis step)
S2 second step (step of deriving ash melting point of coal)
10 S3 third step (step of selecting metal species to be
supported and deriving amount thereof to be supported)
S4 fourth step (supporting step)
S5 fifth step (pyrolysis step)
18

CLAIMS:
1. A method for preparing blast furnace injection coal to be
injected through a tuyere into an interior of a blast
furnace main body of a blast furnace 5 installation, the
method comprising:
a first step of analyzing ash of run-of-mine coal
and weight percentages of Al, Si, Ca, and Mg in the ash;
a second step of deriving an ash melting point of
10 the coal based on data obtained by the analysis;
a third step of selecting a metal species to be
supported on the coal and deriving the amount of the metal
species to be supported based on data obtained in the
first step and the second step to adjust the ash melting
15 point of the coal to 1200 to 1400°C;
a fourth step of supporting the metal in the amount
to be supported onto the coal by an ion exchange method;
and
a fifth step of pyrolyzing the coal obtained in the
20 fourth step.
2. The method for preparing blast furnace injection coal
according to claim 1, wherein
the metal is at least one of calcium and magnesium.
3. The method for preparing blast furnace injection coal
25 according to claim 1 or 2, wherein
the coal is thermally treated at 350 to 550°C in
the fifth step to adjust a residual volatile content to
15 to 35%.
4. The method for preparing blast furnace injection coal
19
according to any one of claims 1 to 3, wherein
the amount of the metal to be supported on the coal
is 0.2 to 1.55 in terms of (CaO+MgO)/SiO2 weight ratio.
5. The method for preparing blast furnace injection coal
5 according to claim 4, wherein
the amount of the metal to be supported on the coal
is 0.25 to 1.4 in terms of (CaO+MgO)/SiO2 weight ratio.
6. The method for preparing blast furnace injection coal
according to claim 5, wherein
10 the amount of the metal to be supported on the coal
is 0.35 to 1 in terms of (CaO+MgO)/SiO2 weight ratio.
7. Blast furnace injection coal, which is obtained by the
method for preparing blast furnace injection coal
according to any one of claims 1 to 6.
15 8. A method for using blast furnace injection coal, the method
comprising injecting blast furnace injection coal
obtained by the method for preparing blast furnace
injection coal according to any one of claims 1 to 6 through
a tuyere into an interior of a blast furnace main body of
20 a blast furnace installation.