TECHNICAL FIELD
The present invention relates to a method for preparing blast furnace blow-in
5 coal.
BACKGROUND ART
Blast furnace installations have been configured so as to be capable of
10 producing pig iron from iron ore by charging a starting material such as iron ore,
limestone, or coke from the top of the blast furnace main body into the interior and
blowing hot air and blast furnace blow-in coal (pulverized coal) as auxiliary fuel
from a tuyere on the bottom side on the side of a blast furnace main body.
15 To stably operate the above blast furnace installation, the blast furnace blowin
coal must suppress accretion of blast furnace blow-in ash or occlusion by that
blast furnace blow-in ash in a pathway leading to the tuyere of the blast furnace
main body.
20 For example, it has been proposed to improve combustibility of blast furnace
blow-in coal by adding a CaO-based flux such as limestone or serpentinite to
pulverized coal of which the softening point of the pulverized coal ash is less than
1300°C, thereby adjusting the softening point of the ash in the pulverized coal to
higher than or equal to 1300°C, and then blowing only the pulverized coal of which
25 the softening point of the pulverized coal ash is higher than or equal to 1300°C into
the interior from a tuyere of a blast furnace main body (for example, refer to Patent
Document 1 below).
Furthermore, a blast furnace operating method has been proposed, wherein,
30 for example, any one or two or more types of CaO-based, MgO-based and Si02-
based flux are blown into the interior of a blast furnace from a tuyere (for example,
refer to Patent Document 2 below).
CITATION LIST
Patent Literature
5 Patent Document 1 : Japanese Unexamined Patent Application Publication No.
H05-156330A
Patent Document 2: Japanese Unexamined Patent Application Publication No.
H03-029131A
10 SUMMARY OF INVENTION
Technical Problem
However, the powdered coal (blast furnace blowing coal) described in Patent
Document 1 causes an increase in running cost because only the powdered coal of
15 which the ash softening point has been adjusted to higher than or equal to 1300°C
by intentionally adding the flux described above to powdered coal is used. Also,
since the flux is only calcium oxide, the addition quantity of the flux becomes
extremely large depending on the ash composition of the single pulverized coal(s),
*
and there i3 the possibility of causing a decrease in the amount of heat release of
20 the blast furnace blow-in coal depending on the addition quantity thereof.
In Patent Document 2, described is only a blast furnace operating method
which assures fluidity of bosh slag produced in the blast furnace by setting the
viscosity at 1450°C to less than or equal to 10 poise. Therefore, there is the
25 possibility that accretion of blast furnace blow-in ash or occlusion by the blast
furnace blow-in ash in a pathway leading to the tuyere of the blast furnace main
body cannot be suppressed. Furthermore, due to the fact that flux is added, there is
the possibility of causing a decrease in the amount of heat release of the blast
furnace blow-in coal depending on the addition quantity thereof.
3 0
From such facts, the present invention was devised to solve the problems
described above, and an object of the present invention is to provide a method for
preparing blast furnace Mow-in coal that can provide, at a low cost, blast furnace
blow-in coal that suppresses occlusion by blast furnace blow-in ash or accretion of
35 blast furnace blow-in ash in a pathway leading to a tuyere of a blast furnace main
body, while suppressing a decrease in the amount of heat release.
Solution to Problem
The method for preparing blast furnace blow-in coal pertaining to the first
invention which solves the above problems is a method for preparing blast furnace
5 blow-in coal blown from a tuyere into an interior of a blast furnace main body of a
blast furnace installation, the method comprising: a first step of analyzing a
moisture content of run-of-mine coal, ash of the coal, and weight percentages of Al,
Si, Ca and Mg in the ash; a second step of selecting, on the basis of data obtained
by analysis, a first coal type, of which the moisture content in the run-of-mine coal
10 is greater than or equal to 15% by weight, and, when the total of Al, Si, Ca and Mg
oxides in the ash is taken as 100% by weight, the A1203 content is 20% by weight *
5% by weight, the CaO content is greater than or equal to 20% by weight and less
than or equal to 40% by weight, and the MgO content is less than or equal to 10%
by weight; a third step of selecting, on the basis of data obtained by analysis, a
15 second coal type in that, when the total weight of Al, Si, Ca and Mg oxides in that
ash is taken as 100% by weight, the A1203 content is 20% by weight k 5% by
weight, the CaO content is greater than or equal to 40% by weight, and the MgO
content is less than or equal to 10% by weight; a fourth step of deriving a mixing
ratio of the first coal type and the second coal type that results in the CaO content
20 in the ash of mixed coal resulting from mixing the first coal type and the second
coal type being greater than or equal to 40% by weight, on the basis of the CaO
content in the ash of the first coal type when the total weight of Al, Si, Ca and Mg
oxides in that ash is takeh as 100% by weight and the A1203 content in that ash is
taken as 20% by weight, and on the basis of the CaO content in the ash of the
25 second coal type when the total weight of Al, Si, Ca and Mg oxides in that ash is
taken as 100% by weight and the A1203 content in that ash is taken as 20% by
weight; and a fifth step of mixing the first coal type and the second coal type in the
mixing ratio.
3 0 The method for preparing blast furnace blow-in coal pertaining to the second
invention which solves the above problems is the method for preparing blast
furnace blow-in coal pertaining to the first invention described above, having a
sixth step of pyrolyzing the mixed coal resulting from mixing the first coal type and
the second coal type.
35
The method for preparing blast furnace blow-in coal pertaining to the third
invention which solves the above problems is the method for preparing blast
furnace blow-in coal pertaining to the first invention described above, having a
pretreatment step of separately pyrolyzing the first coal type and the second coal
type, performed before the fifth step, and a seventh step of molding the mixed coal,
performed after the fifth step.
5
Advantageous Effects of Invention
By the method for preparing blast furnace blow-in coal pertaining to the
present invention, it is possible to obtain, at a low cost, blast furnace blow-in coal
10 that suppresses occlusion by blast furnace blow-in ash or accretion of blast furnace
blow-in ash in a pathway leading to a tuyere of a blast furnace main body, while
suppressing a decrease in the amount of heat release.
9
Brief Description of Drawings
15
FIG. 1 is a flowchart illustrating a procedure of a method for preparing blast
furnace blow-in coal pertaining to an embodiment of the present invention.
FIG. 2 is a quaternary phase diagram for Si02-Ca0-Mg0-20% A1203 when
the total weight of Al, Si, Ca and Mg oxides in the ash of the mixed coal used in the
20 method for preparing blast furnace blow-in coal pertaining to an embodiment of the
present invention is taken as 100% by weight and the A1203 content is taken as 20%
by weight.
FIG. 3 is a quaternary phase diagram for SO2-Ca0-Mg0-20% A1203 used
for describing a confirmation test of the method for preparing blast furnace blow-in
25 coal pertaining to the working example of the present invention.
Description of Embodiments
Embodiments of the method for preparing blast furnace blow-in coal
30 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.
An embodiment of the method for preparing blast furnace blow-in coal
35 pertaining to the present invention will be described based on FIGS. 1 and 2.
The blast furnace blow-in coal pertaining to this embodiment is blast furnace
blow-in coal blown from a tuyere into the interior of a blast furnace main body of a
blast furnace installation, which, as illustrated in FIG. 1, can be easily prepared by
analyzing the moisture content of run-of-mine coal and the ash of the coal, and
5 analyzing the weight percentages of Al, Si, Ca and Mg in the ash of the coal (first
step Sl); selecting a low-ash-melting-point first coal type satisfying conditions A
(second step S2); selecting a high-ash-melting-point second coal type satisfying
conditions B which differ from conditions A (third step S3); deriving a mixing ratio
for mixing these coals (first coal type and second coal type) (fourth step S4); and
10 mixing the selected first coal type and the second coal type in that mixing ratio
(fifth step S5).
In the first step S1, the moisture content of run-of-mine coal and the
composition of the ash of the coal are the data most basically used as the quality of
15 coal (run-of-mine coal), and are obtained by, for example, the industrial analysis set
forth in JIS M 8812 (2004) implemented when the run-of-mine coal is produced or
used.
In the first step S1, the weight percentages of Al, Si, Ca and Ma in the ash of
20 the coal are the data most basically used as the quality of coal (run-of-mine coal),
and are obtained by, for example, the analysis method of metal in exhaust gas set
forth in JIS K 0083 (method by ICP (high-frequency inductively coupled plasma))
or the analysis method of coal ash and coke ash set forth in JIS M 8815
implemented when the run-of-mine coal is produced or used.
25
Conditions A in the second step S2 are that the moisture content of the runof-
mine coal is greater than or equal to 15% by weight, and, as illustrated in FIG. 2,
when the total of Al, Si, Ca and Mg oxides in the ash is taken as 100% by weight,
the A1203 content is 20% by weight * 5% by weight, the CaO content is greater
30 than or equal to 20% by weight and less than or equal to 40% by weight, and the
MgO content is less than or equal to 10% by weight..
Examples of run-of-mine coal of the first coal type satisfying conditions A
are generally low-grade coals (oxygen atom content (dry base): greater than 18% by
35 weight; average pori diameter: from 3 to 4 nm) having a low ash melting point (for
example, 1200°C), such as lignite, sub-bituminous coal, bituminous coal, and the
like. Other coals that may be used include pyrolyzed coals, specifically those
having an oxygen atom content (dry base) of from 10 to 18% by weight, which has
been greatly reduced by desorption of tar-producing groups such as oxygencontaining
functional groups (carboxyl groups, aldehyde groups, ester groups,
hydroxyl groups, and the like), specifically those in which decomposition
(reduction) of the main skeleton (combustion components of mainly C, H, 0) has
been greatly suppressed, and having an average pore diameter of from 10 to 50 nm
by means of removing moisture by heating (from 110 to 200°C for from 0.5 to 1
hour) low-grade coal in a low-oxygen atmosphere (oxygen concentration: less than
or equal to 5% by volume) to dry it, and then removing water, carbon dioxide, tar
and the like as pyrolyzed gas or pyrolyzed oil by pyrolysis while heating (from 460
to 590°C (preferably from 500 to 550°C) for from 0.5 to 1 hour) in a low-oxygen
atmosphere (oxygen concentration: less than or equal to 2% by volume), and then
cooling (lower than or equal to 50°C) in a low-~xygen atmosphere (oxygen
concentration: less than or equal to 2% by volume).
Conditions B in the third step S3 are that, as illustrated in FIG. 2, when the
total of Al, Si, Ca and Mg oxides in the ash is taken as 100% by weight, the A1203
content is 20% by weight * 5% by weight, the CaO content is greater than or equal
to 40% by weight, and the MgO content is less than or equal to 10% by weight.
Examples of run-&-mine coal of the second coal type satisfying conditions
B are generally low-grade coals having a moisture content of greater than or equal
to 15% by weight (oxygen atom content (dry base): greater than 18% by weight;
average pore diameter: from 3 to 4 nm) having a low ash melting point (for
example, 1200°C), such as lignite, sub-bituminous coal, bituminous coal and the
like, but are not limited to high-grade coals having a moisture content of less than
15% by weight. Other coals that may be used include pyrolyzed coals, specifically
those having an oxygen atom content (dry base) of from 10 to 18% by weight,
which has been greatly reduced by desorption of tar-producing groups such as
oxygen-containing functional groups (carboxyl groups, aldehyde groups, ester
groups, hydroxyl groups and the like), specifically those in which decomposition
(reduction) of the main skeleton (combustion components of mainly C, H, 0) has
been greatly suppressed, and having an average pore diameter of from 10 to 50 nm
by means of removing moisture by heating (from 110 to 200°C for from 0.5 to 1
hour) low-grade coal in a low-oxygen atmosphere (oxygen concentration: less than
or equal to 5% by volumi) to dry it, and then removing water, carbon dioxide, tar
and the like as pyrolyzed gas or pyrolyzed oil by pyrolysis while heating (from 460
to 590°C (preferably from 500 to 550°C) for from 0.5 to 1 hour) in a low-oxygen
atmosphere (oxygen concentration: less than or equal to 2% by volume), and then
cooling (lower than or equal to 50°C) in a low-gxygen atmosphere (oxygen
concentration: less than or equal to 2% by volume).
5
In the fourth step S4, as the mixing ratio of the first coal type and the second
coal type, on the basis of the ash composition data of the first coal type obtained in
the first step S1, the CaO content in the ash of the first coal type is derived when
the total weight of Al, Si, Ca, and Mg oxides in the ash of the first coal type is
10 taken as 100% by weight and the A1203 content in that ash is taken as 20% by
weight, and, on the basis of the ash composition data of the second coal type
obtained in the first step S1, the CaO content in the ash of the second coal type is
derived when the total weight of Al, Si, Ca and Mg oxides in the ash of the second
coal type is taken as 100% by weight and the A1203 content in that ash is taken as
15 20% by weight, and, on the basis of the CaO content in the ash of the first coal type
and the CaO content in the ash of the second coal type, the mixing ratio that results
in the CaO content in the ash of mixed coal resulting from mixing the first coal
type and the second coal type being greater than or equal to 40% by weight is
derived.
20
In the fifth step S5, blast furnace blow-in coal is prepared by mixing the first
coal type selected in the second step S2 and the second coal type selected in the
third step S3 in the mixing ratio derived in the fourth step S4.
25 Because the blast furnace blow-in coal produced by the method for preparing
blast furnace blow-in coal pertaining to this embodiment is a mixed coal of the first
coal type satisfying conditions A and the second coal type satisfying conditions B
mixed in a mixing ratio that results in the CaO weight in the ash of the mixed coal
being greater than or equal to 40% by weight when the total of Al, Si, Ca and Mg
30 oxides in the ash of the mixed coal of the first coal type and the second coal type is
taken as 100% by weight and the A1203 content in the ash is taken as 20% by
weight, the ash melting point of the blast furnace blow-in coal is from 100 to 150°C
higher than the temperature of the hot air blown into the interior from the tuyere of
the blast furnace main body and the ash of blast furnace blow-in coal (blast furnace
35 blow-in ash) does not melt by the hot air, and as a result, it can suppress accretion
of blast furnace blow-in ash or occlusion by the blast furnace blow-in ash in the
pathway leading to the tuyere of the blast furnace main body.
For this reason, with the blast furnace blow-in coal pertaining to this
embodiment, simply mixing the first coal type and the second coal type and causing
the CaO content in the ash of the mix coal obtained by mixing the first coal type
5 and the second coal type to be greater than or equal to 40% by weight results in the
ash melting point of the mixed coal being higher than or equal to 1400°C despite
containing a low-ash-melting-point first coal type, and as a result, there is no need
to add an additive such as calcium oxide to the coal, and therefore, a decrease in the
amount of heat release due to addition of the additive does not occur, and a
10 decrease in the amount of heat release of the obtained blast furnace blow-in coal
can be suppressed.
Therefore, by the method for preparing blast furnace blow-in coal pertaining
to this embodiment, it is possible to obtain, at a low cost, blast furnace blow-in coal
15 that suppresses accretion of blast furnace blow-in ash or occlusion by blast furnace
blow-in ash in a pathwaj, leading to a tuyere of a blast furnace main body while
suppressing a decrease in the amount of heat release.
EXAMPLES
20
Working examples performed to confirm the operation and effect of the
method for preparing blast furnace blow-in coal 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 run-of-mine coal and
the ash of the coal are analyzed, ancl the weight percentages of Al, Si, Ca and Mg in
the ash of the coal are analyzed in advance (first step Sl), a first coal type
satisfying conditions A is selected (second step S2), and a second coal type
30 satisfying conditions B different from conditions A is selected (third step S3). In
this working.example, coal type 1 shown in Table 1 below was selected as the first
coal type satisfying conditions A, and coal type 2 shown in Table 1 below was
selected as the second coal type satisfying conditions B.
'Table 11
l~oal /coal type/
kotalof Si02, Al2O3, CaO and MgO b? 176.91 172.47 1
4sh
:omposition
5
When the total weight of Al, Si, Ca and Mg oxides in the ash of coal type 1
was taken as 100% by yyeight and the A1203 content was converted to 20% by
weight, the contents of Si, Ca and Mg oxides in the ash of coal type 1 were the
values shown in Table I above. Thus, the ash melting point of coal type 1 is
10 positioned at point P1 in FIG. 3, which is a quaternary phase diagram for Si02-
10
'4
Si02
A1203
Ti02
Fe203
-
CaO
MgO
-Si02 (as converted when Si02, A1203,
CaO and MgO total 100 wt%)
A1203 (as converted when Si02, A1203,
CaO and MgO total 100 wt%)
CaO (as converted when Si02, A1203, CaO
Units
wt%
wt%
wt%
wt%
wt%
wt%
41.2
22.4
29.8
24.7
19.5
45.8
type 1
31.7
17.2
1.34
5.98
22.9
5.11
10.0
24.5
45.5
9.9
and MgO total 100 wt%)
MgO (as converted when Si02, A1203,
2
17.9
14.1
0.87
7.34
33.2
7.27
CaO and MgQ total 100 wt%)
Si02 (as converted when Si02, CaO arLd
MgO total 80 wt%)
CaO (as converted when Si02, CaO and
%
42.47
30.72
MgO total 80 wt%)
MgO (as converted when Si02, CaO and
MEO total 80 wt%)
Ca0-Mg0-20% A1203 when the total of Al, Si, Ca and Mg oxides in the ash of the
coal is taken as 100% by weight and the A1203 coptent is converted to 20% by
weight.
When the total weight of Al, Si, Ca and Mg oxides in the ash of coal type 2
was taken as 100% by weight and the A1203 content was converted to 20% by
weight, the contents of Si, Ca and Mg oxides in the ash of coal type 2 were the
values shown in Table 1 above. Thus, the ash melting point of coal type 2 is
positioned at point P2 in FIG. 3.
10
Then, a mixing ratio of the first coal type and the second coal type that
results in the CaO content in the ash of mixed coal resulting from mixing the first
coal type and the second coal type being greater than or equal to 40% by weight is
derived, on the basis of the CaO content in the ash of the first coal type when the
15 total weight of Al, Si, Ca and Mg oxides in that ash is taken as 100% by weight and
the A1203 content in that ash is taken as 20% by weight, and on the basis of the
CaO content in the ash of the second coal type when the total weight of Al, Si, Ca
and Mg oxides in that ash is taken as 100% by weight and the A1203 content in that
ash is converted to 20% by weight. In this working example, the mixing ratio of
20 coal type 1 is 30% by weight, and the mixing ratio of coal type 2 is 70% by weight.
A blast furnace blow-in coal consisting of a mixed coal resulting from mixing coal
type 1 in a ratio of 30% by weight and coal type 2 in a ratio of 70% by weight was
used as test substance 1.
When. the total of Al, Si, Ca and Mg oxides in the ash of test substance 1 was
taken as 100% by weight and the A1203 content was converted to 20% by weight,
the contents of Si, Ca and Mg oxides in the ash of test substance 1 were the values
shown in Table 2 below. Thus, the ash melting point of test substance 1 is
positioned at point P3 in FIG. 3, and it is clear that the ash melting point P3 of test
30 substance 1 is positioned in a region in which the ash melting point of coal is
higher than or equal to 1400°C.
hg0 (as converted when Si02, CaO and MgO total 80 wt%)
[Table 21
Thus, it is clear that by this working example, it is possible to obtain, at low
cost, blast furnace blow-in coal that suppresses accretion of blast furnace blow-in
5 ash or occlusion by blast furnace blow-in ash in a pathway leading to a tuyere of a
blast furnace main body while suppressing a decrease in the amount of heat release
despite containing low-ash-melting-point coal, by analyzing a moisture content of
run-of-mine coal, ash of $he coal, and the weight percentages of Al, Si, Ca and Mg
Si02 (as converted when Si02, CaO and MgO total 80 wt%)
CaO (as converted when Si02, CaO and MgO total 80 wt%)
in the ash of the coal; selecting a first coal type satisfying conditions A, and
10 selecting a second coal type satisfying conditions B which differ from conditions A;
deriving a mixing ratio of the first coal type and the second coal type that results in
the CaO content in the ash of mixed coal resulting from mixing the first coal type
and the second coal type being greater than or equal to 40% by weight, on the basis
of the CaO content in the ash of the first coal type when the total weight of Al, Si,
15 Ca and Mg oxides in that ash is taken as 100% by weight and the A1203 content in
that ash is taken as 20% by weight, and on the basis of the CaO content in the ash
of the second coal type when the total weight of Al, Si, Ca and Mg oxides in that
ash is taken as 100% by weight and the A1203 content in that ash is taken as 20% by
weight; and mixing the first coal type and the second coal type in the mixing ratio
20 to obtain mixed coal.
Test
substance
1
3 0
4 1
[Other Embodiments]
*
Furthermore, a method for preparing blast furnace blow-in coal in which the
third step S3 is performed after the second step S2 was described above, but a
25 method for preparing blast furnace blow-in coal in which the second step S2 and
the third step S3 are performed simultaneously, or a method for preparing blast
furnace blow-in coal in which the second step S2 is performed after the third step
S3, may also be used.
A method for preparing blast furnace blow-in coal that provides blast
furnace blow-in coal by performing the first step S1 to the fifth step S5 was
described above, but a method for preparing blast furnace blow-in coal that
provides blast furnace blow-in coal by performing a pyrolysis step, wherein the
5 mixed coal .is simultaneously pyrolyzed (heated in a low-oxygen atmosphere
(oxygen concentration: less than or equal to 2% by volume) from 460 to 590°C
(preferably from 500 to 550°C) for from 0.5 to 1 hour) in the same pyrolysis device
(pyrolysis means), as a sixth step S6 after performing the first step S1 to the fifth
step S5, may also be used. By such a method for preparing blast furnace blow-in
10 coal, it is possible to obtain blast furnace blow-in coal that not only exhibits the
same actions and effects as the embodiments described above, but also has had its
combustibility improved immediately before being blown into the interior from the
tuyere of the blast furnace main body.
15 Furthermore, a method for preparing blast furnace blow-in coal that provides
blast furnace blow-in coal by performing a pyrolysis step, wherein the first coal
type and the second coal type are pyrolyzed (heated in a low-oxygen atmosphere
(oxygen concentration: less than or equal to 2% by volume) from 460 to 590°C
(preferably from 500 to 55O0C) for from 0.5 to 1 hour) in separate pyrolysis devices
20 (pyrolysis means), as a pretreatment step after the first step S1 to fourth step S4, in
other words, before the fifth step S5, and then performing a molding step as a
seventh step S7 performed after the fifth step S5, wherein a binder (for example,
corn starch, molasses, asphalt or the like) and water and the like are added to the
pyrolyzed mixed coal which is then molded, may also be used. By such a method
25 for preparing blast furnace blow-in coal, it is possible to easily obtain blast furnace
blow-in coal that not only exhibits the same actions and effects as the embodiments
described above, but also has improved ease of handling.
Industrial Applicability
30
The method for preparing blast furnace blow-in coal pertaining to the
present invention can be used extremely advantageously in the iron-making
industry because it can, at a low cost, provide blast furnace blow-in coal that
suppresses occlusion by blast furnace blow-in ash or accretion of blast furnace
35 blow-in ash in a pathway leading to a tuyere of a blast furnace main body.
WE CLAIM:
1. A method for preparing blast furnace blow-in coal blown from a tuyere into an
5 interior of a blast furnace main body of a blast furnace installation, the method
comprising:
a first step of analyzing a moisture content of run-of-mine coal, ash
of the coal, and weight percentages of Al, Si, Ca and Mg in the ash;
a second step of selecting, based on data obtained by analysis, a first
10 coal type, of which the moisture content of the run-of-mine coal is greater than
or equal to 15% by weight, and, when a total of Al, Si, Ca and Mg oxides in the
ash is taken as 100% by weight, an A1203 content is 20% by weight * 5% by
weight, a CaO content is greater than or equal to 20% by weight and less than
or equal to 40% by weight, and an MgO content is less than or equal to 10% by
15 weight;
a third step of selecting, based on data obtained by analysis, a second
coal type, of which, when the total of Al, Si, Ca and Mg oxides in the ash is
taken as 100% by weight, the A1203 content is 20% by weight * 5% by weight,
the CaO content is greater than or equal to 40% by weight, and the MgO
20 content is less than or equal to 10% by weight;
a fourth step of deriving a mixing ratio of the first coal type and the
second coal type that results in the CaO content in the ash of mixed coal
resulting from mixing the first coal type and the second coal type being greater
than or equal to 40% by weight, based on the CaO content in the ash of the first
25 coal type when the total weight of Al, Si, Ca and Mg oxides in that ash is taken
as 100% by weight and the A1203 content in that ash is taken as 20% by weight,
and based on the CaO content in the ash of the second coal type when the total
weight of Al, Si, Ca and Mg oxides in that ash is taken as 100% by weight and
the A1203 content in that ash is taken as 20% by weight; and
30 a fifth step of mixing the first coal typi and the second coal type in
the mixing ratio.
2. The method for preparing blast furnace blow-in coal according to claim 1,
further comprising
35 a sixth step of pyrolyzing the mixed coal resulting from mixing the
first coal type and the second coal type.
3. The method for preparing blast furnace blow-in coal according to claim 1,
further comprising
a pretreatment step of separately pyrolyzing the first coal type and the
second coal type, which is performed before the fifth step; and a seventh step
5 of molding the mixed coal, which is performed after the fifth step.