[Technical Field]
[0001]
The present invention relates to a method for preparing blast furnace blow-in coal. [Background Art] [0002]
Blast furnace installations have been configured so as to be capable of 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. [0003]
To stably operate the above blast furnace installation, the blast furnace blow-in coal must suppress accretion of blast furnace blow-in ash or blockage by that blast furnace blow-in ash in a pathway leading to the tuyere of the blast furnace main body. [0004]
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 not less than 1300°C, and then blowing only the pulverized coal of which the softening point of the pulverized coal ash is not less than 1300°C into the interior from a tuyere of a blast furnace main body (for example, refer to Patent Document 1 below). [0005]
Furthermore, a blast furnace operating method has been proposed, wherein, 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). [Prior Art Document] [Patent Documents] [00061

[Patent Document 1] Japanese Unexamined Patent Application'Publication No.
H05-156330A
[Patent Document 2] Japanese Unexamined Patent Application Publication No.
H03-029131A
[Summary of the Invention]
[Problems to be Solved by the Invention]
[0007]
However, with the powdered coal (blast furnace blow-in coal) described in Patent Document 1, although the ash softening point can be adjusted to not less than 1300°C by adding flux together with a single pulverized coal or mixed pulverized coal when blowing, the flux is only calcium oxide, and as a result, the addition quantity of the flux becomes extremely large depending on the ash composition of the single pulverized coal(s), and there is the possibility of causing a decrease in the amount of heat generation of the blast furnace blow-in coal depending on the addition quantity thereof. [0008]
Additionally, in Patent Document 1, when the mixed pulverized coal is constituted of a coal having a high weight ratio of Si02 in the ash, for example, an Si02 content in the ash of not less than 70% by weight, and a low-ash-melting-point coal having a high weight ratio of CaO in the ash, for example, an Si02 content in the ash of not less than 35% by weight and not greater than 45% by weight, there is the possibility that the ash melting point of the obtained pulverized coal (blast furnace blow-in coal) cannot be increased and accretion of blast furnace blow-in ash or blockage by the blast furnace blow-in ash in a pathway leading to the tuyere of the blast furnace main body cannot be suppressed even if the compounding ratio of these coals is adjusted and calcium oxide flux is added to the mixed pulverized coal. [0009]
In Patent Document 2, described only is a blast furnace operating method which assures fluidity of bosh slag produced in the blast furnace by setting the viscosity at 1450°C to not greater than 10 poise. Therefore, there is the possibility that accretion of blast furnace blow-in ash or blockage by the blast furnace blow-in ash in a pathway leading to the tuyere of the blast furnace main body cannot be suppressed. [0010]
From such facts, the present invention was devised to solve the problems described above, and an ohiect of the present invention is to provide a method Tor pfepaTiiig'l5last'fufn3ceiyiSW^fh c5trtlfetican°provi'dF'W'as'l"'iurnaice Wow-iri

coa] that suppresses accretion of blast furnace bJow-in ash or blockage by the biast 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 generation despite containing low-asb-melting-point coal. {Means for Solving the Problems] [0011]
A method for preparing blast furnace blow-in coal pertaining to a first invention that solves the problems described above is a method for preparing blast furnace blow-in coal blown from a tuyere into the interior of a blast furnace main body of a blast furnace installation. The method comprising: a first step of analyzing the moisture content of run-of-mine coal, the ash of the coal, and the 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 of the run-of-mine coal is less than 15% by weight, and the total weight of Al, Si, Ca and Mg oxides in the ash is not less than 70% by weight of the ash weight, and, when the total of Al, Si, Ca and Mg oxides in the ash is taken as 100% by weight, an AI2O3 content is 20% by weight ± 5% by weight, and an Si02 content is not less than 70% by weight; a third step of selecting, on the basis of data obtained by analysis, a second coal type, of which the moisture content of the run-of-mine coal is not less than 15%) by weight, and the total weight of Al, Si, Ca and Mg oxides in the ash is not less than 70% by weight of the ash weight, and, when the total of Al, Si, Ca and Mg oxides in the ash is taken as 100%) by weight, the AI2O3 content is 20% by weight ± 5% by weight, and the SJO2 content is not less than 35% by weight and not greater than 45% by weight, and an MgO content is not less than 0% by weight and not greater than 25% by weight; a fourth step of deriving an ash melting point of a mixed coal obtained by mixing the selected first coal type and the second coal type, on the basis of a four-dimensional state diagram for SiO2-CaO-MgO-20%) AI2O3 when the total of Al, Si, Ca and Mg oxides in the ash of the mixed coal is taken as 100% by weight and the AljOj content is converted to 20% by weight; a fifth step of selecting SiOa, MgO or CaO as an additive to cause the ash melting point of the mixed coal to be not less than J400°C when added to the mi.xed coal in the smallest quantity, on the basis of the ash melting point of the mixed coal and the four-dimensional state diagram for SiO2-CaO-MgO-20%) AI2O3; a sixth step of deriving an addition quantity of the selected additive to the mixed coal; a seventh step of mixing the selected first coal tvoe and the secondxaaU
siepot adding the additive in the addition quantity to the mixed coal.
K-Ki^S

[0012]
A method for preparing blast furnace blow-in coal pertaining to a second invention that solves the problems described above is the method for preparing blast furnace blow-in coal pertaining to the first invention described above, wherein, in the fifth step, the CaO is selected as the additive upon the ash melting point of the mixed coal being within a region that is not greater than HOCC in the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 when the total of Al, Si, Ca and Mg oxides in the ash of the mixed coal is taken as 100% by weight and the AI2O3 content is converted to 20% by weight, and being below a first boundary line according to equation (1), which represents the relationship between a content x of the Si02 and a content y of the CaO; the SiOa is selected as the additive upon the ash melting point of the mixed coal being within a region that is not greater than MOCC in the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3, and being above a second boundary line according to equation (2), which represents the relationship between the SvOi content x and the CaO content y; and the MgO is selected as the additive upon the ash melting point of the mixed coal being within a region that is not greater than 1400°C in the four-dimensional state diagram for Si02-CaO-MgO-20% AI2O3, and being above the first boundary line and below the second boundary line.
y = 0.083x^-6.67x+166.3 (1)
y = 0.065x^-6.86x+177.4 . (2) [Effects of the Invention] [0013]
By the method for preparing blast furnace blow-in coal pertaining to the present invention, it is possible to obtain blast furnace Wow-in coaJ that suppresses accretion of blast furnace blow-in ash or blockage 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 generation despite containing low-ash-melting-point coal. [Brief Description of the Drawings] [0014]
[Fig. 1] FIG. 1 is a flowchart illustrating a procedure of a method for preparing blast furnace blow-in coal pertaining to a first embodiment of the present invention.
[Fig. 2] FIG 2 is a four-dimensional state diagram for SiO2-CaO-MgO-20% AIJOT, for the ash of the blast_fixmac£Jhl ■^tf^imeH^fnie presenTinvention.

[Fig. 3] FIG. 3 is a four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 for the ash of the blast furnace blow-in coal pertaining to a second embodiment of the present invention,
[Fig. 4] FIG. 4 is a diagram used for deriving a first boundary line in FIG. 3. [Fig. 5] FIG. 5 is a diagram used for deriving a second boundary line in FIG. 3. [Fig. 6] FIG. 6 is a four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 used for describing a confirmation test of the method for preparing blast furnace blow-in coal pertaining to the embodiments of the present invention. [Modes for Carrying Out the Invention] [0015]
Embodiments of the method for preparing blast furnace blow-in 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. [0016] [First Embodiment]
A first embodiment of the method for preparing blast furnace blow-in coal pertaining to the present invention will be described based on FIGS. 1 and 2. [0017]
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, the ash of the coal, and the weight percentages of Al, Si, Ca and Mg in the ash of the coal (first step SI); selecting a first coal type satisfying conditions A (second step S2); selecting a second coal type with a low ash melting point satisfying conditions B different from conditions A (third step S3); deriving the ash melting point of the mixed coal obtained by mixing these coals (first coal type and second coal type) (fourth step S4); selecting an additive on the basis of the ash melting point of the mixed coal and a four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 (fifth step S5); deriving an addition quantity of the selected additive (sixth step S6); mixing the selected first coal type and the second coal type to result in mixed coal (seventh step S7); and adding the additive in the addition quantity to the mixed coal (eighth step S8). [0018]
In the first step SI, the moisture content of run-of-mlne coal and the
;o'ar^B"tBeo&ta most Basi'cally used as the
re

quality of 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. f00]9]
In the first step SI, the weight percentages of AI, Si, Ma and Ca in the ash of 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 HS 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. [0020]
Conditions A in the second step S2 are that the moisture content of the run-of-mine coal is less than 15% by weight, and the total weight of Al, Si, Ca and Mg oxides in the ash is not less than 70% by weight of the ash 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 AI2O3 content is 20% by weight ± 5% by weight, and the SiOa content is not less than 70% by weight. [0021]
Conditions B in the third step S3 are that the moisture content of the run-of-mine coal is not less than 15% by weight, and the total weight of Al, Si, Ca and Mg oxides in the ash is not less than 70% by weight of the ash 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 AI2O3 content is 20% by weight ± 5% by weight, and the Si02 content is not less than 35% by weight and not greater than 45% by weight, and the MgO content is not less than 0% by weight and not greater than 25% by weight. [0022]
Examples of run-of-mine coal of the second coal type satisfying conditions B are generally low-grade coals (oxygen atom content (dry base): more 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. Other coals that may be used include dry-distilled 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), ^pecjficallyjtho^Jn_whach_decoj^^ "(tafift&iKtiSffToInponents"oTmainIy~C7H, O) 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: not greater than 5% by volume) to dry it, and then removing water, carbon dioxide, tar and the like as dry-distilled gas or dry-distilled oil by dry distillation 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: not greater than 2% by volume), and then cooling (not higher than 50°C) in a low-oxygen atmosphere (oxygen concentration: not greater than 2% by volume). [0023]
In the fourth step S4, the weight ratio of Si02, CaO and MgO in the ash of the mixed coal is determined on the basis of the ash composition data of the first coal type obtained in the first step SI, the ash composition data of the second coal type obtained in the first step SI, and the mixing proportion of the first coal type and the second coal type, by taking the total of AI, Si, Ca and Mg oxides in the ash of the mixed coal as 100% by weight and converting the AI2O3 content in the ash of the mixed coal to 20% by weight. On the basis of the weight ratio of SiOj, CaO and MgO in the ash of the mixed coal and a four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 illustrated in FIG. 2, the ash melting point of the mixed coal is derived. The mixing proportion of the first coal type and the second coal type may be set as appropriate; for example, it is advantageous when the second coal type is not less than 25% by weight, [0024]
In the fifth step SS, on the basis of the ash melting point of the mixed coal derived in the fourth step S4 and the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 illustrated in FIG. 2, one type of Si02, MgO or CaO is selected as an additive to cause the ash melting point of the mixed coal to be not less than 1400°C, which is higher than the hot air (1200°C) blown into the interior from the tuyere on the bottom side on the side of the blast furnace main body of the blast furnace installation, when added to the mixed coal in the smallest quantity (addition quantity). Examples of Si02 sources include silica stone, clay and the like. Examples of MgO sources include MgO powder, natural minerals, dolomite, magnesium carbonate and the like. Examples of CaO sources include quicklime, limestone, serpentinite and the like. r00251

In the sixth step S6, the addition quantity of the additive to the mixed coal is derived on the basis of the ash melting point of the mixed coal derived in the fourth step S4, the four-dimensional state diagram for SiOi-CaO-MgO-20% AI2O3 illustrated in FIG. 2, and the additive selected in the fifth step S5. [0026]
In the eighth step S8, blast furnace blow-in coal is prepared by adding the additive selected in the fifth step S5 to the mixed coal in the addition quantity derived in the sixth step S6. [0027]
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, and because the additive selected on the basis of the ash melting point of the mixed coal and a four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 has been added in the addition quantity to the mixed coal^, 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 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 blockage by the blast furnace blow-in ash in the pathway leading to the tuyere of the blast furnace main body. [0028]
For this reason, with the blast furnace blow-in coal pertaining to this embodiment, because the additive is selected from SiOz, MgO or CaO and the addition quantity of the selected additive is derived, the addition quantity of the additive can be reduced even though the ash melting point of the mixed coal obtained by mixing the first coal type and the second coal type is lowered to less than ]400°C, unlike the case where only calcium oxide can be selected as an additive. As a result, a decrease in the amount of heat generation of the obtained blast furnace blow-in coal can be suppressed. [0029]
Therefore, by the method for preparing blast furnace blow-in coal pertaining to this embodiment, it is possible to obtain blast furnace blow-in coal that suppresses accretion of blast furnace blow-in ash or blockage by blast furnace blow-in ash in a pathway leading to a tuyere of a blast furnace main body while suppressing a decreasejnjhe amo^gl^^^ttjgagcglkja^d^pij© ^^Sf^^^T^^^-merfing-point coal.

[0030]
Additionally, because one type of SiOa, CaO or MgO can he selected as the additive, unlike conventional pulverized coal (blast furnace blow-in coal) obtained by adding calcium oxide as fiux together with single pulverized coal or mixed pulverized coal, the ash melting point of the blast furnace blow-in coal obtained by adding the additive to a mixed coal of the first coal type and the second coal type can be increased to not less than 1400°C, despite containing a first coal type of which the SiOz content in the ash is not less than 70% by weight and a low-ash-melting-point second coal type of which the SiO2 content in the ash is not less than 35% by weight and not greater than 45% by weight. [0031] (Second Embodiment]
A second embodiment of the method for preparing blast furnace blow-in coal pertaining to the present invention will be described based on FIG. 1 and FIGS. 3 to 5.
This embodiment employs a procedure illustrated in FIG. 1 in which the fifth step S5 of the first embodiment has been modified. The other steps are roughly the same as those illustiated in FIG. 1, and duplicate descriptions will be omitted as appropiiate. [0032]
In this embodiment, in the fifth step S5 of selecting the additive added to the mixed coal, first, it is specified where the ash melting point of the mixed coal derived in the fourth step S4 performed prior to the fifth step S5 is positioned in the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 when the total of Al, Si, Ca and Mg oxides in the ash of the coal is taken as 100% by weight and the AI2O3 content is converted to 20% by weight, illustrated in FIG. 3. In short, it is specified where the ash melting point of the mixed coal is positioned in region D encompassed by the solid line in FIG. 3, which is the region in which the ash melting point of coal is not greater than I400°C. Furthermore, if the ash melting point of the mixed coal is positioned outside region D, the mixed coal can be used as blast furnace blow-in coal without additvg the additive to the mixed coal because the ash melting point of that tnixed coal is higher than HOO°C. [0033]
Next, a first boundary line LI which results in the smallest addition quantity ofjh£addithLe,il^derivg4by^,d^^

the basis of the four-dimensional state diagram for SiO2-CaO-MgO-20% AhQi
illustrated in FIG. 3.
[0034]
The first boundary line LI, as illustrated in FIGS, 3 and 4, is a curve that satisfies, for example, equation (1) representing the relationship between Si02 content x and CaO content y, which passes through the location where the SiOz content is 35% by weight and the CaO content is 35% by weight, and the location where the Si02 content is 41% by weight and the CaO content is 33% by weight, and the location where the SiOj content is 45% by weight and the CaO content is 35% by weight, when the total of AI, Si, Ca and Mg oxides in the ash of the coal is taken as 100% by weight.
y = 0.083x^-6.67x+166.3 (1)
[0035]
A second boundary line L2 which results in the smallest addition quantity of the additive is derived by selecting SiOi or MgO as the additive on the basis of the fout-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 illustrated in FIG. 3. [0036]
The second boundary line L2, as illustrated in FIGS. 3 and 5, is a curve that satisfies, for example, equation (2) representing the relationship between SiOa content x and CaO content y, which passes through the location where the SiOa content is 60% by weight and the CaO content is 0% by weight, and near the location where the Si02 content is 63% by weight and the CaO content is 3% by weight, and near the location where the SiOj content is 65% by weight and the CaO content is 7% by weight, and near the lociation where the Si02 content is 67% by weight and the CaO content is 9% by weight, and near the location where the SiOj content is 68% by weight and the CaO content is 12% by weight, when the total of Al, Si, Ca and Mg oxides in the ash of the coal is taken as 100% by weight.
y = 0.065x^-6.86x+177.4 (2)
[0037]
In short, in the fifth step 85, the CaO is selected as the additive upon the ash melting point of the mixed coal being within region D, which is not greater than 1400°C in the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 when the total of Al, Si, Ca and Mg oxides in the ash of the mixed coal is taken as 100% and the AI2O3 content is converted to 20% by weight, illustrated in FIG. 3, and being below the first homiiMxJin&J~J,,S££mdmg.i(h^iS^S^^.
rgguTi, itls possibletocause the ash melting point of the blast furnace

blow-in coal obtained by adding CaO as the additive to the mixed coal to be not Jess than 1400°C, despite the CaO addition quantity being lower than in cases where another additive such as SiaO or MgO is added. [0038]
In the fifth step S5, the SiOz is selected as the additive upon the ash melting point of the mixed coal being within region D, which is not greater than 1400°C in the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 when the total of Al, Si, Ca and Mg oxides in the ash of the mixed coal is taken as 100% and the AI2O3 content is converted to 20% by weight, illustrated in FIG. 3, and being above a second boundary line L2 according to equation (2). As a result, it is possible to cause the ash melting point of the blast furnace blow-in coal obtained by adding Si02 as the additive to the mixed coal to be not less than 1400°C, despite the SiOa addition quantity being lower than in cases where another additive such as CaO or MgO is added. [0039]
In the fifth step S5, the MgO is selected as the additive upon the ash melting point of the mixed coal being within region D, which is not greater than 1400°C in the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 when the total of Al, Si, Ca and Mg oxides in the ash of the mixed coal is taken as 100% and the AI2O3 content is converted to 20% by weight, illustrated in FIG. 3, and being above the first boundary line LI and below the second boundary line L2. As a result, it is possible to cause the ash melting point of the blast furnace blow-in coal obtained by adding MgO as the additive to the mixed coal to be not Jess than 1400°C, despite the MgO addition quantity being lower than in cases where another additive such as SiOi or CaO is added. [0040]
Thus, the position of the ash melting point of the mixed coal derived in the fourth step 84 in the four-dimensional state diagram for Si02-CaO-MgO-20% AI2O3 illustrated in FJG. 3 is derived, and on the basis of the position of the ash melting point of the mixed coal, the additive can be selected and the addition quantity of the additive can be derived, and as a result, the additive can be more reliably selected and the addition quantity of the additive can be more reliably derived. [0041]
Therefore, by the method for preparing blast furnace blow-in coal pertaining to this embodiment, it is possible to obtain blast furnace blow-in
coal that suppresses accretion of blast furaacjeJbd.QW.ziii-ashjM:-bl«.cka«©rbjfeblas4^
-- - - - '" %g^ ~ :
^-m ash m a pathway leading to a tuyere or a blast furnace main

body while suppressing a decrease in the amount of heat generation despite
containing low-ash-melting-point coal, more reliably than in the embodiment
described previously.
[EXAMPLES]
[0042]
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. [0043]
First, as illustrated in FIG. 1, the moisture content of run-of-mine coal and 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 SI), a first coal type satisfying conditions A is selected (second step S2), and a second coal type 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 I below was selected as the second coal type satisfying conditions B. [0044] [Table 1]

Coal type 1 Coal type 2
Units
Ash composition Si02 wt.% 31.7 70.3

AI2O3 wt.% 17.2 23.7

TiOa wt.% 1.34 1.14

FezOa wt.% 5.98 4.47

CaO wt.% 22.9 0.6

MgO wt.% 5.11 0.6

NaiO wt.% 1.4 0.42

K2O wt.% 0.42 1.35

SO3 wt.% 9.36 -

P2O3 wt.% 0.88 -

Total of Si02, AI2O3, CaO and MgO wt.% 76.91 95.2

Si02 (as converted when Si02, AI2O3, CaO and MgO total 100 wt.%) wt.% 41.2 73.8

AI2O3 (as converted when Si02, AI2O3, CaO and MgO total 100 wt.%) wt.% 22.4 24.9

CaO (as converted when Si02, AI2O3, CaO and MgO total 100 wt.%) wt.% 29.8 0.6

MgO (as converted when Si02, AI2O3, CaO and MgO total 100 wt.%) wt.% 6.6 0.6

Si02 (as converted when Si02, CaO and MgO total 80 wt.%) wt.% 42.47 78.72

CaO (as converted when Si02, CaO and MgO total 80 wt.%) wt.% 30.72 0.64

MgO (as converted when Si02, CaO and MgO total 80 wt.%) wt.% 6.8 0.64
[0045]
When the total of Al, Si, Ca and Mg oxides in the ash of coal type 1 was taken as 100% by weight and the AI2O3 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 1 above. Thus, the ash melting point of coal type 1 is positioned at point PI in FIG. 6, which is a four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 when the total of Al, Si, Ca and Mg oxides in the ash of the coal is taken as 100% by weight and the AI2O3 content is converted

[0046]
When the total of Al, Si, Ca and Mg oxides in the ash of coal type 2 was taken as 100% by weight and the AI2O3 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. 6. [0047]
Here, when the total of Al, Si, Ca and Mg oxides in the ash of the mixed coal was taken as 100% by weight and the AI2O3 content was converted to 20% by weight, the contents of Si, Ca and Mg oxides in the ash of the mixed coal obtained by mixing coal type 1 and coal type 2 were the values shown in Table 2 below. Thus, the ash melting point of the mixed coal is positioned at point P3 in FIG. 6. In short, the ash melting point of the mixed coal is positioned within region D, which is not greater than 1400°C. [0048] [Table 2]

Mixed coal (wt.%)
Ash composition Si02 (as converted when SiOa, AI2O3, CaO and MgO total 100 wt.%) 57.5

AI2O3 (as converted when Si02, AI2O3, CaO and MgO total 100 wt.%) 23.6

CaO (as converted when Si02, AI2O3, CaO and MgO total 100 wt.%) 15.2

MgO (as converted when Si02, AI2O3, CaO and MgO total 100 wt.%) 3.6

Total of Si02, AI2O3, CaO and MgO 100.0

Si02 (as converted when Si02, CaO and MgO total 80 wt.%) 60.3

CaO (as converted when Si02, CaO and MgO total 80 wt.%) 15.9

MgO (as converted when Si02, CaO and MgO total 80 wt:%) 3.8

Total of Si02, CaO and MgO 80.0
[0049]
Blast furnace blow-in coal obtained by selecting Si02 as an additive and adding 25% by weight Si02 to the above mixed coal even though the ash melting point P3 of the mixed coal is positioned at a location where MgO is to be selected as the additive in the method for preparing blast furnace blow-in coal pertainingJ54hfiL;S,e$§g€t^i>©!di^^ tronrpafative substance 1. When the total ot Al, Hi, Ua and Mg oxides in the ash

of comparative substance 1 was taken as 100% by v^'eight and the AI2O3 content was converted to 20% by weight, the contents of Si, Ca and Mg oxides in the ash of comparative substance 1 were the values shown in Table 3 below. Thus, the ash melting point of comparative substance I is positioned at point P4 in FIG. 6, and it is clear that the ash melting point P4 of comparative substance 1 is positioned within region D, in which the ash melting point of coal is not greater than 1400°C. [0050}
Blast furnace blow-in coal obtained by selecting CaO as an additive and adding 25% by weight CaO to the above mixed coal was used as comparative substance 2. When the total of Al, Si, Ca and Mg oxides in the ash of comparative substance 2 was taken as 100% by weight and the A{:id3 content was converted to 20% by weight, the contents of Si, Ca and Mg oxides in the ash of comparative substance 2 were the values shown in Table 3 below. Thus, the ash melting point of comparative substance 2 is positioned at point P5 in FIG. 6, and it is clear that the ash melting point P5 of comparative substance 2 is positioned within region D, in which the ash melting point of coal is not greater than 1400°C. [OOSl]
Blast furnace blow-in coal obtained by selecting MgO as an additive and adding 25% by weight MgO to the above mixed coal because the ash melting point P3 of the mixed coal is positioned at a location where MgO is to be selected as the additive in the method for preparing blast furnace blow-in coal pertaining to the second embodiment described above, was used as test substance 1. When the total of Al, Si, Ca and Mg oxides in the ash of test substance I was taken as 100% by weight and the AI2O3 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 3 below. Thus, the ash melting point of test substance I is positioned at point P6 in FIG 6, and it is clear that the ash melting point P6 of test substance I is positioned in a region in which the ash melting point of coa] is not greater than I400°C. [0052] [Table 31

Test
substance
1 Comparative substance 1 Comparative substance 2
Ash composition Si02 (as converted when Si02, AiiOs, CaO and MgO total 100 wt.%) 46.0 66.0 46.0

Ai203 (as converted when Si02, AI2O3, CaO and MgO total 100 wt.%) 18.9 18.9 18.9

CaO (as converted when Si02, AI2O3, CaO and MgO total 100 wt.%) 12.2 12.2 32.2

MgO (as converted when Si02, AI2O3, CaO and MgO total 100 wt.%) 22.9 2.9 2.9

Total of Si02, AI2O3, CaO and MgO 100.0 100.0 100.0

Si02 (as converted when Si02, CaO and MgO total 80 wt.%) 45.4 65.1 45.4

CaO (as converted when Si02, CaO and MgO total 80 wt.%) 12.0 12.0 31.7

MgO (as converted when Si02, CaO and MgO total 80 wt.%) 22.6 2.9 2.9

Total of Si02, CaO and MgO 80.0 80.0 80.0
[0053]
Thus, it is clear that by this working example, it is possible to obtain blast furnace blow-in coal that suppresses accretion of blast furnace blow-in ash or blockage 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 generation despite containing low-ash-melting-point coal, by analyzing the moisture content of run-of-mine coal, the ash of the coal, and the weight percentages of Al, Si, Ca and Mg in the ash of the coal; selecting a first coal type satisfying conditions A; selecting a second coal type satisfying conditions B different from conditions A; deriving the ash melting point of the mixed coal obtained by mixing these coals (first coal type and second coal type) on the basis of a four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 when the total of Al, Si, Ca and Mg oxides in the ash of the mixed coal is taken as 100% by weight and the AI2O3 content is converted to 20% by weight; selecting Si02, MgO or CaO as an additive to cause the ash melting point of the mixed coal to be not less than 1400°C when added to the mixed coal in the smallest quantity on the basis of the ash melting point of the mixed coal and a four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3; deriving an addition ■^q^3^aB#t^fe®fefe£addteyeg5imi3igs^flFlits£^

result in mixed coal; and adding the additive in the addition quantity to the
mixed coal.
[0054]
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 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 82 is performed after the third step S3, may also be used. [Industrial Applicability] [0055]
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 provide blast furnace blow-in coal that suppresses accretion of blast furnace blow-in ash or blockage 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 generation despite containing low-ash-melting-point coal. [Explanation of Reference Numerals] [0056]
A Conditions of first coal type B Conditions of second coal type
D Region of ash melting point of mixed coal not greater than I400°C LI First boundary line L2 Second boundary line PI Ash melting point of coal type 1 P2 Ash melting point of coal type 2 P3 Ash melting point of mixed coal (coal types 1, 2) P4 Ash melting point of comparative substance 1 P5 Ash melting point of comparative substance 2 P6 Ash melting point of test substance 1
51 First step (analysis step)
52 Second step (first coal type selection step)
53 Third step (second coal type selection step)
54 Fourth step (mixed coal ash melting point derivation step)
55 Fifth step (additive selection step)
56 Sixth step (addition quanlitJi^ dfiEJ^atigajiS^
57 S'evenfh step (inixing step)

S8 Eighth step (addition step)

WE CLAIMS:-
A method for preparing blast furnace 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 is less than 15% by weight, and a total weight of Al, Si, Ca and Mg oxides in the ash is not less than 70% by weight of the ash weight, and, when the total of Al, Si, Ca and Mg oxides in the ash is taken as 100% by weight, an AI2O3 content is 20% by weight ± 5% by weight, and an SiOi content is not less than 70% by weight;
a third step of selecting, on the basis of data obtained by analysis, a second coal type, of which the moisture content in the run-of-mine coal is not less than 15% by weight, and the total weight of Al, Si, Ca and Mg oxides in the ash is not less than 70% by weight of the ash weight, and, when the total of Al, Si, Ca and Mg oxides in the ash is taken as 100% by weight, the AI2O3 content is 20% by weight ± 5% by weight, and the SiOa content is not less than 35% by weight and not greater than 45%) by weight, and an MgO content is not less than 0% by weight and not greater than 25% by weight;
a fourth step of deriving an ash melting point of a mixed coal obtained by mixing the selected first coal type and the second coal type, on the basis of a four-dimensional state diagram for SiO2-CaO-MgO-20%) AI2O3 when the total weight of Al, Si, Ca and Mg oxides in the ash of the mixed coal is taken as 100% by weight and the AI2O3 content is converted to 20% by weight;
a fifth step of selecting Si02, MgO or CaO as an additive to cause the ash melting point of the mixed coal to be not less than 1400°C when added to the mixed coal in the smallest quantity, on the basis of the ash melting point of the mixed coal and the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3;
a sixth step of deriving an addition quantity of the selected additive to the mixed coal;
a seventh step of mixing the selected first coal type and the second coal type to result in mixed coal; and
an eizhth step^QSijsiddia.sUh&rM4i^^^ Ttnxea coat.

[Claim 2]
The method for preparing blast furnace blow-in coaf according to claim 1, wherein,
in the fifth step,
the CaO is selected as the additive upon the ash melting point of the mixed coal being within a region not greater than 1400°C in the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3 when the total of AI, Si, Ca and Mg oxides in the ash of the mixed coal is taken as 100% by weight and the AI2O3 content is converted to 20% by weight, and being below a first boundary line according to equation (1) representing a relationship between a content x of the SiOa and a content y of the CaO;
the SiOa is selected as the additive upon the ash melting point of the mixed coal being within a region not greater than HOC^C in the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3, and being above a second boundary line according to equation (2) representing a relationship between the SiOa content x and the CaO content y; and
the MgO is selected as the additive upon the ash melting point of the mixed coal being within a region not greater than 1400°C in the four-dimensional state diagram for SiO2-CaO-MgO-20% AI2O3, and being above the first boundary line and below the second boundary line:
y = 0.083x' - 6.67x + 166.3 (1) y = O.OeSx-^ - 6.86x + 177.4 (2)