[0001]The present invention relates to a blast furnace operation method.
Priority is claimed on Japanese Patent Application No. 2019-026220, filed on
February 18, 2019, the content of which is incorporated herein by reference.
[Related Art]
[0002]
In the steel industry, a blast furnace method is the mainstream of a steelmaking
process. In the blast furnace method, iron-bearing materials for a blast furnace (raw
materials including iron oxide; mainly sintered ores; hereinafter simply referred to as
"iron-bearing materials") and coke are alternately charged in layers into a blast furnace
from the top of the blast furnace, and hot blast is blown into the blast furnace from a
tuyere of a blast furnace lower part. The hot blast reacts with pulverized coal blown
together with the hot blast and the coke in the blast furnace such that high-temperature
reducing gas (here, mainly CO gas) is produced in the blast furnace. That is, the hot
blast gasifies the coke and the pulverized coal in the blast furnace. The reducing gas
rises in the blast furnace and reduces the iron-bearing material while heating the ironbearing
materials. The iron-bearing materials are heated and reduced by the reducing
gas while falling in the blast furnace. Next, the iron-bearing materials are melted and
are dropped into the blast furnace while being further reduced by the coke. Finally, the
iron-bearing materials are accumulated in a hearth as molten iron (pig iron) including
about 5 mass% of carbon. The molten iron in the hearth is extracted from a tap hole
and is provided for the next steelmaking process. Accordingly, in the blast furnace
- 1 -
method, a carbon material such as coke or pulverized coal is used as a reducing
material.
[0003]
Incidentally, recently, global warming has been a social problem, and reduction
in emissions of carbon dioxide (C02 gas) that is one greenhouse effect gas has been
claimed as a countermeasure against global warming. As described above, in the blast
furnace method, a large amount of pig iron is manufactured using a carbon material as a
reducing material. Therefore, a large amount of C02 is produced. Accordingly, the
steel industry is a main industry regarding C02 gas emissions and need to meet the
demand of society. Specifically, further reduction in the reducing material ratio (the
amount of reducing material used per ton of molten iron is urgently required in the blast
furnace operation. Specifically, the reducing material ratio refers to the total mass of
coke and pulverized coal required for producing one ton of molten iron (and when
reducing gas is blown from a tuyere, reducing gas (described below blown from a
tuyere).
[0004]
The reducing material has a function of heating materials to be charged into the
furnace as a heat source and a function of reducing the iron-bearing material in the
furnace, and needs to increase the reduction efficiency in the furnace for reducing the
reducing material ratio. Reduction reactions in the furnace can be represented by
various reaction formulae. Among these reduction reactions, a direct reduction
reaction (reaction formula: FeO + C ~ Fe + Co) by coke is an endothermic reaction
accompanied by high absorption of heat. Accordingly, in order to reduce the reducing
material ratio, it is important to suppress the occurrence of the direct reduction reaction
as far as possible. The reason for this is that, by suppressing the occurrence of the
- 2 -
direct reduction reaction as far as possible, the amount of coke and a reducing material
used as a heat source required for the direct reduction reaction can be reduced. The
direct reduction reaction occurs in a blast furnace lower part. Therefore, as long as the
iron-bearing materials can be sufficiently reduced by reducing gas such as CO or H2
until the iron-bearing materials reach the furnace lower part, the iron-bearing materials
as a target of the direct reduction reaction can be reduced.
[0005]
As techniques in the related art for solving the above-described problem, for
example, as disclosed in Patent Documents 1 to 3, a technique of improving the
reducing gas potential in a furnace by blowing reducing gas (for example, COG, LPG,
or methane gas) including carbon together with hot blast from a tuyere is known. In
this technique, carbon in the reducing gas blown from a tuyere is converted into CO gas
in the blast furnace to reduce the iron-bearing materials. As a result, the amount of the
iron-bearing materials as a target of the direct reduction reaction can be reduced. In
the following description, unless specified otherwise, "carbon" and "hydrogen"
represent "carbon atom" and "hydrogen atom", respectively.
[Prior Art Document]
[Patent Document]
[0006]
[Patent Document 1] Japanese Patent No. 6019893
[Patent Document 2] Japanese Patent No. 5070706
[Patent Document 3] Japanese Unexamined Patent Application, First
Publication No. 2007-169750
[Disclosure of the Invention]
[Problems to be Solved by the Invention]
- 3 -
[0007]
However, when the amount of reducing gas including carbon blown (the
amount thereof blown per ton of molten iron) increases, the amount of carbon fed into
the blast furnace increases together with an increase in the amount of the reducing
material blown. Together with an increase in the reducing gas volume, the CO gas
utilization factor in the blast furnace changes. When the reducing gas volume
increases excessively, most of the reducing gas is exhausted without being used in the
furnace. Accordingly, only when the amount of reducing gas blow increases, carbon
in the reducing gas is exhausted without being used for reduction such that the reducing
material ratio may increases or C02 emissions may increase.
[0008]
Thus, the present invention has been made in consideration of the abovedescribed
problems, and object of the present invention is to provide a novel and
improved blast furnace operation method in which a desired a reducing material ratio
reduction effect can be obtained.
[Means for Solving the Problem]
[0009]
In order to achieve the object, the present inventors defined a parameter
reduction Input~C in specific carbon consumption caused by blowing reducing gas into
the blast furnace. Here, the specific carbon consumption Input C (kg/t-pig) refers to
the amount of carbon consumed per ton of molten iron and more specifically refers to
the total mass of coke, pulverized coal, and carbon in the reducing gas blown from the
tuyere required for producing one ton of molten iron. Specifically, Input Cis
calculated from the following Numerical Expression (1).
[0010]
- 4 -
Input C (kg/t-pig) =Coke Ratio (kg/t-pig) x Carbon Proportion (mass%) in
Coke+ Pulverized Coal Ratio (kg/t-pig) x Carbon Proportion (mass%) in Pulverized
Coal+ Consumption of Reducing Gas Used (Nm3/t-pig) x Carbon Proportion (kg/Nm3
)
in Reducing Gas ( 1)
[0011]
Here, the coke ratio and the pulverized coal ratio refer to the amounts of coke
and pulverized coal used per ton of molten iron. The consumption of reducing gas
used refers to the reducing gas volume per ton of molten iron. The carbon proportion
in coke refers to mass% of carbon with respect to the total mass of the coke, and the
carbon proportion in pulverized coal refers to mass% of carbon with respect to the total
mass of the pulverized coal. The carbon proportion in reducing gas refers to the
carbon content per unit volume of the reducing gas. In Numerical Expression (1 ), the
volume (Nm3 /t-pig) of the reducing gas blown to manufacture one ton of molten iron
was used as the consumption of reducing gas used, and the carbon content (kg/Nm3) per
unit volume of reducing gas was used as the carbon proportion in the reducing gas.
However, the mass (kg/t-pig) of the reducing gas blown to manufacture one ton of
molten iron was used as the consumption of reducing gas used, and mass% of carbon
with respect to the total mass of the reducing gas was used as the carbon proportion in
the reducing gas.
[0012]
Input~C can be defined, for example, as the proportion of reduction
(percentage, %) in specific carbon consumption (Input C) of an operation where a
predetermined amount of reducing gas is blown with respect to a base operation. In
the base operation, for example, operation conditions where the reducing gas is not
blown can be set. When Input C of a base operation is represented by A (kg/t-pig) and
- 5 -
Input C of an operation where a predetermined amount of reducing gas is blown is
represented by B (kg/t-pig), Input~C is represented by the following Numerical
Expression (2). Of course, the reduction Input~C in specific carbon consumption is
not limited to a value represented by the following Numerical Expression (2) and may
be a value representing the degree of reduction in specific carbon consumption with
respect to the base operation. For example, Input~C may be the difference (A - B)
between A and B.
Input~C =(A- B) I Ax 100 (%) (2)
[0013]
Input~C is the parameter corresponding to the reducing material ratio, and as
Input~C increases, the reduction in reducing material ratio with respect to the base
operation increases. As described below in Examples in detail, the present inventors
calculated Input~C with respect to the amounts of a plurality of reducing gas blown by
performing a blast furnace operation simulation while changing the type of the reducing
gas and the amount of the reducing gas blown (the amount of the reducing gas blown
per tone of molten iron). As a result, as long as the amount of the reducing gas blown
is small, Input~C increases together with an increase in the amount of the reducing gas
blown. However, it was clarified that, as the amount of the reducing gas blown further
increases, the increase in Input~C decreases, and Input~C starts to decrease.
[0014]
Thus, the present inventors conducted an investigation on parameters that
affect Input~C or the reducing material ratio. First, the present inventors focused on
the amount of hydrogen fed (Nm3/t-pig) into the blast furnace per ton of molten iron.
The hydrogen described herein refers to hydrogen fed into the front of the tuyere and
includes not only hydrogen in the reducing gas but also hydrogen in hygroscopic
- 6 -
moisture of air and hydrogen in pulverized coal. The present inventors changed the
amount of hydrogen fed by changing the type of the reducing gas and the amount of the
reducing gas blown and acquires a correlation between the amount of hydrogen fed and
a hydrogen reduction rate(%) at this time through the blast furnace operation
simulation. Here, the blast furnace operation simulation was performed using the
same method as that of Example 1 below. The hydrogen reduction rate is defined as
the proportion of iron oxide reduced by hydrogen in iron oxide fed into the furnace, and
the sum of a CO reduction rate (the proportion of iron oxide reduced by CO gas) and a
direct reduction rate (the proportion of iron oxide reduced by direct reduction with C) is
100%. The results are shown in FIG. 2. In FIG. 2, coke oven gas (COG), natural gas
(NG), and mixed gas of coke oven gas and hydrogen gas were used as the reducing gas.
Here, during the mixing of coke oven gas and hydrogen gas for the mixed gas, COG:H2
= 1:1.43 when the total amount of hydrogen fed into the furnace;::::; 270 Nm3/t-pig, and
COG:H2 = 1:2.28 when the total amount of hydrogen fed into the furnace;::::; 340 Nm3/tplg.
In the base operation, the reducing gas was not blown. As a result, it can be
seen that, irrespective of the type of the reducing gas, as the amount of hydrogen fed
increases, the hydrogen reduction rate(%) increases substantially monotonically.
When the iron-bearing materials are completely reduced, the sum of the hydrogen
reduction rate, the CO reduction rate, and the direct reduction rate is 100%, and there is
a relation where, as the hydrogen reduction rate increases, the direct reduction rate (or
the CO reduction rate) decreases. FIG. 3 shows the direct reduction rate at this time.
In this test, as the amount of hydrogen fed increases, the hydrogen reduction rate
increases monotonically, the direct reduction rate decreases monotonically, and
Input~C increases monotonically together with an increase in the amount of hydrogen
fed. Therefore, a specific behavior that the increase in Input~C decrease together with
- 7 -
an increase in the amount of hydrogen fed and Input~C starts to decrease is not likely to
occur. Accordingly, it was found that the amount of hydrogen fed is not a parameter
that affects the behavior of Input~C or the reducing material ratio.
[0015]
Next, the present inventors focused on the consumption of carbon fed into the
blast furnace together with the reducing gas blown from the tuyere. Here, the
consumption of carbon fed into the blast furnace together with the reducing gas is a
value obtained by multiplying the carbon proportion (kg/Nm3) in the reducing gas by
the reducing gas volume (Nm3/t-pig) per ton of molten iron. Hereinafter, the
consumption of carbon fed into the blast furnace together with the reducing gas will
also be referred to as "the carbon consumption in the reducing gas".
[0016]
The present inventors calculated Input~C by performing the blast furnace
operation simulation while changing the carbon consumption in the reducing gas and
the type of the reducing gas as described below in Examples in detail. As a result, the
present inventors found that there is a correlation between Input~C and the carbon
consumption in the reducing gas.
[0017]
The present inventors conducted an investigation on the correlation between
Input~C and the carbon consumption in the reducing gas and clarified that the
correlation between Input~C and the carbon consumption in the reducing gas tends to
vary between a case where a molar ratio C/H of carbon atoms to hydrogen atoms in the
reducing gas is 0.15 or higher and a case where C/H is lower than 0.15. More
specifically, when C/H in the reducing gas is 0.15 or higher, the correlation between
Input~C and the carbon consumption in the reducing gas is uniquely determined
- 8 -
irrespective of the type of the reducing gas (in other words, irrespective of C/H in the
reducing gas). On the other hand, when C/H in the reducing gas is lower than 0.15, the
correlation between Input~C and the carbon consumption in the reducing gas varies
depending on C/H in the reducing gas. Note that, in all the cases, the correlation
between Input~C and the carbon consumption in the reducing gas is represented by a
graph forming an upwardly convex curve (that is, when the carbon consumption in the
reducing gas is a given value, the maximum value is shown).
[0018]
Accordingly, by acquiring the correlation between Input~C and the carbon
consumption in the reducing gas in advance per C/H in the reducing gas, the carbon
consumption in the reducing gas can be determined such that Input~C is a
predetermined target value or higher based on the correlation. In addition, the amount
of the reducing gas blown into the blast furnace can be adjusted based on the
determined carbon consumption in the reducing gas and the carbon proportion in the
reducing gas. As a result, desired Input~C (that is, Input~C that is the target value or
higher) can be obtained. That is, the desired reducing material ratio reduction effect
can be obtained, and further the reducing material ratio can be reduced more reliably.
Further, according to this correlation, when the carbon consumption in the reducing gas
is a given value, Input~C shows a maximum value (the specific graph will be described
below). Accordingly, when the carbon consumption in the reducing gas is determined
such that Input~C is close to the maximum value, the reducing material ratio can be
more efficiently reduced. Further, by acquiring the correlation per C/H in the reducing
gas, the amount of the reducing gas blown can be determined based on the correlation
corresponding to C/H in the reducing gas. The present inventors completed the
present invention based on the above-described findings.
- 9 -
[0019]
The summary of the present invention is as follows.
[0020]
According to one aspect of the present invention, there is provided a blast
furnace operation method in which reducing gas including hydrogen atoms and carbon
atoms is blown into a blast furnace, the method including: acquiring a correlation
between a carbon consumption in reducing gas and a reduction Input~C in specific
carbon consumption caused by blowing the reducing gas into the blast furnace per
molar ratio C/H of carbon atoms to hydrogen atoms in the reducing gas; determining a
carbon consumption in the reducing gas where the reduction Input~C in specific carbon
consumption is a predetermined target value or higher on the basis of the correlation
acquired per C/H; and adjusting the amount of the reducing gas blown into the blast
furnace on the basis of the determined carbon consumption in the reducing gas and the
carbon proportion in the reducing gas.
[0021]
Here, the molar ratio C/H of the carbon atoms to the hydrogen atoms in the
reducing gas may be 0.15 or higher.
[0022]
In addition, the correlation may be represented by a quadratic expression of the
carbon consumption in the reducing gas.
[0023]
In addition, the correlation may be represented by Y = a1X2 + b1X + c1 (where
X represents the carbon consumption in the reducing gas, Y represents the reduction
Input~C in specific carbon consumption, and all the coefficients a1, b1, and c1
represent values that do not depend on the molar ratio C/H).
- 10 -
[0024]
In addition, the carbon consumption in the reducing gas may be determined in
a range of 21 kg/t-pig to 107 kg/t-pig.
[0025]
In addition, the carbon consumption in the reducing gas may be determined in
a range of 21 kg/t-pig to 65 kg/t-pig.
[0026]
In addition, the molar ratio C/H of the carbon atoms to the hydrogen atoms in
the reducing gas may be higher than 0 and lower than 0.15.
[0027]
In addition, the molar ratio C/H of the carbon atoms to the hydrogen atoms in
the reducing gas may be 0.13 or lower.
[0028]
In addition, the molar ratio C/H of the carbon atoms to the hydrogen atoms in
the reducing gas may be 0.10 or lower.
[0029]
In addition, the correlation may be represented by Y = a2X2 + b2X + c2 (where
X represents the carbon consumption in the reducing gas, Y represents the reduction
Input~C in specific carbon consumption, and at least one of the coefficients a2, b2, and
c2 represents a function including the molar ratio C/H as a variable).
[0030]
In addition, when the reducing gas is blown into the blast furnace, a flame
temperature may be adjusted to be 2000°C or higher.
[0031]
In addition, in order to adjust the flame temperature to be 2000°C or higher, at
- 11 -
least one of an blast volume or an oxgen enrichment ratio in hot blast may be adjusted.
[0032]
In addition, the reducing gas may be selected from the group consisting of coke
oven gas, natural gas, reformed top gas (BFG), city gas, mixed gas thereof, and
hydrogen mixed gas obtained by mixing hydrogen gas therewith.
[Effects of the Invention]
[0033]
According to the aspect of the present invention, the desired reducing material
ratio reduction effect can be obtained.
[Brief Description of the Drawings]
[0034]
FIG. 1 is a graph showing a correlation between Input~C and a carbon
consumption (kg/t-pig) in reducing gas per C/H in the reducing gas.
FIG. 2 is a graph showing a relationship between a hydrogen reduction rate and
the amount of hydrogen fed (Nm3/t-pig) into a blast furnace per ton of molten iron.
FIG. 3 is a graph showing a relationship between a direct reduction rate and the
amount of hydrogen fed (Nm3/t-pig) into a blast furnace per ton of molten iron.
[Embodiments of the Invention]
[0035]
Hereinafter, a preferable embodiment of the present invention will be described
in detail. In the following embodiment, a numerical limitation range represented using
"to" refers to a range including numerical values before and after "to" as a lower limit
and an upper limit. A numerical value shown together with "more than" or "less than"
is not included in a numerical range.
[0036]
- 12 -
<1. Correlation between Input~C and Carbon Consumption in Reducing Gas>
First, a correlation between Input~C and a carbon consumption in reducing gas
blown from a tuyere (hereinafter, the correlation will also be referred to as "~Creducing
gas correlation") will be described based on FIG. 1. In FIG. 1 the vertical
axis (y axis) represents Input~C (%)and the horizontal axis (x axis) represents the
carbon consumption (kg/t-pig) in the reducing gas.
[0037]
Here, Input~C can be defined as the proportion of reduction in specific carbon
consumption caused by blowing the reducing gas into the blast furnace. When Input C
of a base operation is represented by A (kg/t-pig) and Input C of an operation where a
predetermined amount of reducing gas is blown is represented by B (kg/t-pig), Input~C
is represented by the following Numerical Expression (2). Note that Input~C of the
base operation in FIG. 1 is 0.0. Of course, Input~C is not limited to being represented
by the following Numerical Expression (2). For example, the difference (A-B)
between A and B may be acquired as Input~C.
Input~C =(A- B) I Ax 100 (%) (2)
[0038]
The carbon consumption in the reducing gas refers to the consumption of
carbon fed into the blast furnace by the reducing gas blown from the tuyere as described
above, and can be obtained by multiplying the carbon proportion (kg/Nm3) in the
reducing gas by the reducing gas volume (Nm3/t-pig) per ton of molten iron.
[0039]
The reducing gas is blown into the blast furnace from a tuyere provided in the
blast furnace. The reducing gas includes reducing components that reduce ironbearing
materials in the blast furnace. Here, the reducing components according to the
- 13 -
embodiment include not only a component (for example CO gas or hydrogen gas) that
can reduce the iron-bearing materials by itself but also a component (for example, C02
gas or hydrocarbon gas) that can produce reducing gas through a reaction in the blast
furnace (for example, a reaction with coke, pulverized coal, or the like or
decomposition).
[0040]
The ~C-reducing gas correlation shown in FIG. 1 is acquired by performing,
for example, a blast furnace operation simulation. As the blast furnace operation
simulation, for example, a so-called "Blast Furnace Mathematical Model" Kouji
TAKATANI, Takanobu IN ADA, Yutaka UJISA W A, "Three-dimensional Dynamic
Simulator for Blast Furnace", ISIJ International, Vol. 39 (1999), No.1, p.15 to 22 can be
used. In this blast furnace mathematical model, an internal region of the blast furnace
is divided in a height direction, a radial direction, and a circumferential direction to
define a plurality of meshes (small regions), and the behavior of each of the meshes is
simulated. The summary of the blast furnace operation simulation is as follows.
That is, the blast furnace operation simulation is performed using various cases where
C/H in the reducing gas and the amount of the reducing gas blown (the amount thereof
blown per ton of molten iron) are different from each other. The cases also include the
base operation (a case where the reducing gas volume is 0). Here, operation conditions
are adjusted such that the flame temperature and the molten iron temperature are as
constant as possible in the cases. For example, at least one of an blast volume or an
oxgen enrichment ratio in hot blast may be adjusted. Here, the flame temperature
refers an in-furnace temperature in a tip end portion of the tuyere on the inside of the
furnace, and will also be referred to as "tuyere tip temperature". In the actual
operation, the flame temperature is calculated as a tuyere tip theoretical combustion
- 14 -
temperature according to Lamm equation described in "Ironmaking Handbook"
(Chijinshokan Co., Ltd.), Akitoshi SHIGEMI. The hot blast blown into the blast
furnace is gas including air. The hot blast may include hygroscopic moisture and
enriched oxygen in addition to air. Schematically, the oxgen enrichment ratio refers to
the volume proportion of oxygen in the hot blast with respect to the total volume of the
hot blast, and is represented by "Oxgen enrichment ratio (%) = {(Blast volume
[Nm3/min] x 0.2I +Amount of Enriched Oxygen [Nm3/min] I (Blast volume [Nm3/min]
+Amount of Enriched Oxygen [Nm3/min])} x IOO -21. In addition to or instead of the
adjustment of the above-described factors, at least one of a coke ratio or a pulverized
coal ratio may be adjusted. As a result, Input~C and the carbon consumption in the
reducing gas are acquired per case. Incidentally, a point representing Input~C and the
carbon consumption in the reducing gas of each of the cases is plotted on the xy plane
shown in FIG. I. Points PI to P8 are examples of the plotted points. A fitted curve
of each of the plots is acquired using an approximation method such as a least -squares
method or the like. These fitted curves form a graph showing the ~C-reducing gas
correlation. Graphs LIto L5 are examples of the graph showing the ~C-reducing gas
correlation.
[004I]
(I-I. Case where C/H is O.I5 or Higher)
As described above, the correlation between Input~C and the carbon
consumption in the reducing gas, that is, the ~C-reducing gas correlation tends to vary
between a case where a molar ratio C/H of carbon atoms to hydrogen atoms in the
reducing gas is O.I5 or higher and a case where C/H is lower than O.I5. Therefore,
first, the ~C-reducing gas correlation of the case where C/H is O.I5 or higher will be
described based on the points PI to P4 and the graph LI.
- I5 -
[0042]
Here, the point PI represents Input~C and the carbon consumption in the
reducing gas in the base operation (operation where the reducing gas is not blown), the
points P2 and P4 represent Input~C and the carbon consumption in the reducing gas in
an operation where coke oven gas (COG, C/H = O.I86) as the reducing gas is blown,
and the point P3 represents Input~C and the carbon consumption in the reducing gas in
an operation where natural gas (C/H = 0.25) as the reducing gas is blown. The points
PI to P3 were acquired using the same method as that of Example I described below.
The point P4 was acquired using the same method as that of Example I, except that the
flame temperature was set as 2085°C or 23I5°C. The graph LI is a graph showing the
fitted curve of the points of PI to P4, that is, the ~C-reducing gas correlation.
[0043]
Examples of the reducing gas where C/H is O.I5 or higher include COG,
natural gas, city gas, and the like. The reducing gas may be gas obtained by reforming
top gas (BFG) (gas obtained by removing water vapor and C02 gas from top gas).
Among these, the reducing gas including hydrocarbon gas, that is, COG, natural gas,
city gas or the like is preferable. When this reducing gas is used, the hydrocarbon gas
is combusted in the furnace to generate heat of combustion. Therefore, a further
reduction in reducing material ratio can be expected. Further, in an iron mill where a
coke furnace is present, the energy can be provided from the iron mill itself by using
COG. COG is more preferable to the other reducing gases from the viewpoint of
costs. The upper limit of C/H is not particularly limited and, for example, may be 0.3
or lower.
[0044]
The composition of COG used to obtain data of the points P2 and P4 is shown
- I6 -
in Table 1, and the composition of natural gas used to obtain data of the point P3 is
shown in Table 2. These compositions were measured by gas chromatography, a mass
spectrometer, or the like. The numerical values of each of the components shown in
Table 1 and 2 are the molar ratio (more specifically, the ratio between the molar
concentrations (moliL)). Note that C represents the carbon proportion (kg1Nm3) in the
reducing gas. CIH of the COG having the composition shown in Table 1 below is
0.185. The calculation example is as follows.
(0.065 + 0.025 + 0.292 + 0.02 X 2 + 0.008 X 2) I (0.535 X 2 + 0.292 X 4 + 0.02 X 4 +
0.008 X 6) = 0.185
[0045]
In addition, C/H of the natural gas having the composition shown in Table 2
below is 0.271. The calculation example is as follows.
(0.85 + 0.03 X 2 + 0.12 X 2) I (0.85 X 4 + 0.03 X 4 + 0.12 X 6) = 0.271
- 17 -
[0046]
[Table 1]
Example of COG Composition
co C02 H2 N2 CH4 C2H4 C2H6 c C/H
(-) (-) (-) (-) (-) (-) (-) (kg/Nm3
) (-)
0.065 0.025 0.535 0.055 0.292 0.02 0.008 0.23 0.185
[0047]
[Table 2]
Example of Natural Gas Composition
CH4 C2H4 C2H6 c C/H
(-) (-) (-) (kg/Nm3
) (-)
0.85 0.03 0.12 0.62 0.271
[0048]
As can be seen from FIG. 1, the points PI to P4 are present on substantially the
same graph Ll. Accordingly, by acquiring the carbon consumption in the reducing gas
irrespective of the type of the reducing gas (in other words, irrespective of C/H in the
reducing gas), Input~C can be uniquely specified. That is, Input~C and the carbon
consumption in the reducing gas have a correlation that does not depend on C/H, this
correlation is represented by the graph Ll. Further, when the fact that the point P4 is
present on the graph L 1 is taken into consideration, it can be said that the correlation
also does not depend on the flame temperature.
[0049]
Since the graph Ll is represented by an upwardly convex graph, the carbon
consumption in the reducing gas is represented by a quadratic expression. For
- 18 -
example, the graph L1 is represented by the numerical expression Y = a1X2 + b1X + cl.
X represents the carbon consumption in the reducing gas, andY represents Input~C.
All the coefficients a1, b1, and c1 represent values that do not depend on the molar ratio
C/H. In the example of FIG. 1, the graph L1 is represented by the numerical
expression Y = -0.0014X2 +0.194X (that is, a1 = -0.0014, b1 = 0.194, c1 = 0). Of
course, the graph L1 is not limited to being represented by this numerical expression.
[0050]
According to the graph L 1, when the carbon consumption in the reducing gas is
in a range of 65 kg/t-pig or lower, Input~C has a positive correlation with the carbon
consumption in the reducing gas, and when the carbon consumption in the reducing gas
is in a range of higher than 65 kg/t-pig, Input~C has a negative correlation with the
carbon consumption in the reducing gas. In addition, when the carbon consumption in
the reducing gas is about 65 kg/t-pig, Input~C shows a maximum value. Accordingly,
when the carbon consumption in the reducing gas is determined such that Input~C is
close to the maximum value, the reducing material ratio can be further reduced.
[0051]
More specifically, when the carbon consumption in the reducing gas is in a
range of21 kg/t-pig to 107 kg/t-pig, Input~C is approximately 4.0% or higher. In this
case, for example, assuming that the reducing material ratio of the base operation is 3 7 5
kg/t-pig to 500 kg/t-pig, the reducing material ratio is reduced by about 15 kg/t-pig to
20 kg/t-pig or more. This reduction is a significant value in consideration of the daily
fluctuation in reducing material ratio, and the effectiveness of the reduction in reducing
material ratio can be expected. Accordingly, the carbon consumption in the reducing
gas is preferably 21 kg/t-pig to 107 kg/t-pig.
[0052]
- 19 -
Here, when the carbon consumption in the reducing gas is about 65 kg/t-pig,
Input~C shows a maximum value, and when the carbon consumption in the reducing
gas exceeds 65 kg/t-pig, Input~C starts to decrease. That is, the effect of reducing
Input C is lost. For example, the reason for this is presumed to be that the carbon
consumption in the reducing gas is excessively high compared to the amount required
for in-furnace reduction such that the gas utilization factor decreases or to be that,
although the amount of the reducing gas blown increases together with an increase in
the carbon consumption in the reducing gas, under the condition that the flame
temperature is constant, the oxgen enrichment ratio increases together with an increase
in the amount of the reducing gas blown and the amount of the gas blown into the blast
furnace through a hot stove decreases such that the sensible heat of air decreases, or the
like. Accordingly, the carbon consumption in the reducing gas is more preferably 65
kg/t-pig or lower, that is, 21 kg/t-pig to 65 kg/t-pig. In this case, Input~C can be made
to be high (specifically 4.0% or higher) with a smaller amount of the reducing gas
blown.
[0053]
In addition, when the reducing gas in which the carbon proportion (kg/Nm3) is
low (in particular, the reducing gas in which the carbon proportion is lower than 0.6
kg/Nm3) is used, due to the restrictions of the operation, there may be a case where the
carbon consumption in the reducing gas is preferably 65 kg/t-pig or lower.
Hereinafter, the reason for this will be described in detail.
[0054]
In the blast furnace operation, it is necessary that the flame temperature is
maintained at a constant value that is higher than or equal to a predetermined value
(here, the predetermined value varies depending on various factors but is likely to be a
- 20 -
value about 2000°C) as far as possible. The reason for this is that, when the flame
temperature is lower than the predetermined value, the combustibility of pulverized coal
decreases and there is a problem, for example, in that unburnt chart is produced and
deteriorates in-furnace permeability or in that only a part of pulverized coal fed as the
reducing material can be used as the reducing gas (that is produced in the furnace), or
the like. When the carbon proportion (kg/Nm3) in the reducing gas blown from the
tuyere is low, it is necessary to blow a large amount of the reducing gas in order to
adjust the carbon consumption in the reducing gas to be higher than 65 kg/t-pig. As a
result, it is necessary to increase the oxgen enrichment ratio in the hot blast. The
reason for this is presumed to be that, unless the oxgen enrichment ratio is increased,
there may be a case where the flame temperature cannot be maintained at the
predetermined value or higher. Note that, as the oxgen enrichment ratio increases, the
oxygen proportion in the hot blast increases such that pure oxygen is blown. At this
time, the oxgen enrichment ratio reaches the upper limit, and the oxgen enrichment ratio
cannot increase any more.
[0055]
For example, when the carbon consumption in the reducing gas is adjusted to
83 kg/t-pig by using the COG having the composition shown in Table 1, it is necessary
to blow the COG at 350 Nm3/t-pig. In this case, by increasing the oxgen enrichment
ratio to be close to the upper limit, the flame temperature can be maintained at the
predetermined value or higher. However, it is necessary to design operation elements
carefully such that the flame temperature is very close to the predetermined value, and it
is necessary to monitor the elements carefully during the operation. Accordingly, the
operation can be performed, but time and efforts are required for the operation.
Further, when the carbon consumption in the reducing gas is 95 kg/t-pig, it is necessary
- 21 -
to blow the COG at 400 Nm3/t-pig. In this case, even when pure oxygen is blown,
there may be a case where the flame temperature cannot be maintained at the
predetermined value or higher. When the carbon consumption in the reducing gas is
65 kg/t-pig or lower, the amount of the COG blown can be made to be lower than 350
Nm3/t-pig. Therefore, an allowance can be given to the oxgen enrichment ratio and the
flame temperature. Accordingly, when the reducing gas in which the carbon
proportion (kg/Nm3) is low (in particular, the reducing gas in which the carbon
proportion is lower than 0.6 kg/Nm3) is used, the carbon consumption in the reducing
gas is preferably 65 kg/t-pig or lower.
[0056]
On the other hand, when the natural gas (the carbon proportion is 0.6 kg/Nm3
or higher) shown in Table 2 is used, basically, the above-described restrictions are not
present. For example, even when the carbon consumption in the reducing gas is 100
kg/t-pig which is much higher than 65 kg/t-pig, the amount of the reducing gas blow
needs to be only about 170 Nm3/t-pig. In this case, although a decrease in flame
temperature is concerned, the flame temperature can be made to be the predetermined
value or higher by increasing the oxgen enrichment ratio. Accordingly, the carbon
consumption in the reducing gas can be made to be higher than 65 kg/t-pig.
[0057]
Due to the above-described reasons, the point P2 is plotted in a range of 65
kg/t-pig or lower, but the point P3 is plotted in a wider range.
[0058]
When operation conditions other than the above-described conditions change,
the ~C-reducing gas correlation may slightly fluctuation from the graph L1. Even in
this case, however, it is considered that there is no significant fluctuation in the
- 22 -
preferable range of the carbon consumption in the reducing gas.
[0059]
(1-2. Case where C/H is lower than 0.15)
Incidentally, first, the ~C-reducing gas correlation of the case where C/H is
lower than 0.15 will be described based on the points PI and P5 to P8 and the graphs L2
to L5. Here, the point P5 represents Input~C and the carbon consumption in the
reducing gas in a case where C/H in the reducing gas is 0.054, the point P6 represents
Input~C and the carbon consumption in the reducing gas in a case where C/H in the
reducing gas is 0.097, the point P7 represents Input~C and the carbon consumption in
the reducing gas in a case where C/H in the reducing gas is 0.137, and the point P8
represents Input~C and the carbon consumption in the reducing gas in a case where C/H
in the reducing gas is 0.02. The points P5 to P8 were acquired using the same method
as that of Example 2 described below. The graphs L2 to L5 are graphs showing the
fitted curves of the points of P5 to P8, that is, the ~C-reducing gas correlations,
respectively.
[0060]
The present inventors conducted an investigation on the reducing gas (for
example, COG, natural gas, city gas, and the like) in the related art, and C/H in most of
the reducing gas was 0.15 or higher. Therefore, the reducing gas in which C/H is
lower than 0.15 may be produced, for example, by mixing hydrogen gas with reducing
gas in which C/H is 0.15 or higher. The reducing gas in which hydrogen gas is mixed
may be any one as long as it is reducing gas in which C/H is 0.15 or higher, and
examples thereof include COG, natural gas, top gas, city gas, and the like. In addition,
the method of producing the reducing gas is not necessarily limited to this method.
For example, the reducing gas in which C/H is lower than 0.15 may be produced by
- 23 -
mixing reducing gases having different C/H's (specifically, reducing gas in which C/H
is 0.15 or higher and reducing gas in which C/H is lower than 0.02) with each other.
[0061]
As clearly seen from FIG. 1, the points P5 to P8 are present in the graphs L2 to
L5 that are different from each other, respectively. Accordingly, when C/H in the
reducing gas is lower than 0.15, the ~C-reducing gas correlation varies depending on
C/H in the reducing gas. That is, by acquiring C/H in the reducing gas and the carbon
consumption in the reducing gas, Input~C can be uniquely specified. This way,
Input~C and the carbon consumption in the reducing gas have a correlation that
depends on C/H, and the correlation perC/His represented by, for example, the graphs
L2 to L5. Note that all the correlations are represented by the upwardly convex graphs
(that is, when the carbon consumption in the reducing gas is a given value, a maximum
value is shown). It is presumed that, even when the flame temperature fluctuates, there
is substantially no effect on the correlation as in the case where C/H is 0.15 or higher.
[0062]
Since the graphs L2 to L5 are represented by an upwardly convex graph, the
graphs L2 to L5 are represented by a quadratic expression of carbon consumption in the
reducing gas. For example, the graphs L2 to L5 are represented by the numerical
expression Y = a2X2 + b2X + c2. In order to simplify the drawing, FIG. 1 does not
show a curve of a portion where Input~C starts to decrease. X represents the carbon
consumption in the reducing gas, and Y represents Input~ C. Since the shapes of the
graphs L2 to L5 vary depending on C/H in the reducing gas, at least one of the
coefficients a2, b2, and c2 represents a function including C/H in the reducing gas as a
variable. Accordingly, when the carbon consumption in the reducing gas is
determined such that Input~C is close to the maximum value, the reducing material
- 24 -
ratio can be further reduced. As described above, the reason why the graphs L2 to L5
start to decrease from the maximum value is presumed to be that the carbon
consumption in the reducing gas is excessively high compared to the amount required
for in-furnace reduction such that the gas utilization factor decreases or to be that,
although the amount of the reducing gas blown increases together with an increase in
the carbon consumption in the reducing gas, under the condition that the flame
temperature is constant, the oxgen enrichment ratio increases together with an increase
in the amount of the reducing gas blown and the amount of the gas blown into the blast
furnace through a hot stove decreases such that the sensible heat of air decreases, and
the like.
[0063]
The graphs L2 to L5 will be described in more detail. In the range of the
carbon consumption in the reducing gas where Input~C does not reach the maximum
value, as C/H decreases, the slopes of the graphs L2 to L5 increase. That is, an
increase in Input~C relative to a unit increase in the carbon consumption in the reducing
gas Increases. Accordingly, as C/H in the reducing gas decreases, Input~C can be
efficiently increased. More specifically, C/H in the reducing gas is preferably 0.13 or
lower, more preferably 0.10 or lower, and still more preferably 0.05 or lower. The
lower limit of C/H is not particularly limited as long as it is higher than 0.
[0064]
As described above, the correlation is present between Input~C and the carbon
consumption in the reducing gas. This correlation, that is, the ~C-reducing gas
correlation tends to vary between a case where the molar ratio C/H of carbon atoms to
hydrogen atoms in the reducing gas is 0.15 or higher and a case where C/H is lower
than 0.15. That is, when C/H in the reducing gas is 0.15 or higher, the ~C-reducing
- 25 -
gas correlation is uniquely determined irrespective of the type of the reducing gas (in
other words, irrespective of C/H in the reducing gas). On the other hand, when C/H in
the reducing gas is lower than 0.15, the ~C-reducing gas correlation varies depending
on C/H in the reducing gas. Note that, in all the cases, the correlation between
Input~C and the carbon consumption in the reducing gas is represented by the upwardly
convex graph (that is, when the carbon consumption in the reducing gas is a given
value, a maximum value is shown).
[0065]
Accordingly, by acquiring the ~C-reducing gas correlation per C/H in the
reducing gas in advance, the carbon consumption in the reducing gas can be determined
such that Input~C is a predetermined target value or higher based on the correlation.
In addition, the amount of the reducing gas blown into the blast furnace can be adjusted
based on the determined carbon consumption in the reducing gas and the carbon
proportion in the reducing gas. As a result, desired Input~C (that is, Input~C that is
the target value or higher) can be obtained. That is, the desired reducing material ratio
reduction effect can be obtained, and further the reducing material ratio can be reduced
more reliably. The blast furnace operation method according to the embodiment is
made based on the above-described findings.
[0066]
In the above-described example, the ~C-reducing gas correlation is acquired by
performing the blast furnace operation simulation, but the method of acquiring the ~Creducing
gas correlation is not limited thereto. Likewise, in an operation in an actual
furnace (including a real operation and a test operation) or a test operation in a test blast
furnace, the ~C-reducing gas correlation can be acquired by calculating Input~C while
changing the carbon consumption in the reducing gas.
- 26 -
[0067]
<2. Blast Furnace Operation Method>
Next, the blast furnace operation method according to the embodiment will be
described. The blast furnace operation method according to the embodiment includes
first to third processes described below.
[0068]
(2-1. First Process)
In the first process, the ~C-reducing gas correlation is acquired per C/H in the
reducing gas. The method of acquiring the ~C-reducing gas correlation (acquisition
method) is not particularly limited. For example, the ~C-reducing gas correlation can
be acquired by performing the blast furnace operation simulation. As the blast furnace
operation simulation, for example, a so-called "Blast Furnace Mathematical Model"
Kouji TAKATANI, Takanobu INADA, Yutaka UJISAWA, "Three-dimensional
Dynamic Simulator for Blast Furnace", ISIJ International, Vol. 39 (1999), No.1, p.15 to
22 can be used. In this blast furnace mathematical model, an internal region of the
blast furnace is divided in a height direction, a radial direction, and a circumferential
direction to define a plurality of meshes (small regions), and the behavior of each of the
meshes is simulated. Calculation conditions of the blast furnace operation simulation
are not particular! y limited and are preferably determined depending on actual operation
conditions. For example, the flame temperature is preferably 2000°C or higher. Note
that, as described above, even when the flame temperature changes, the ~C-reducing
gas correlation does not substantially fluctuate. By performing the blast furnace
operation simulation, the ~C-reducing gas correlation is acquired perC/H. That is, a
graph showing the ~C-reducing gas correlation is acquired. Here, as described above,
the ~C-reducing gas correlation tends to vary between a case where C/H in the reducing
- 27 -
gas is 0.15 or higher and a case where C/H in the reducing gas is lower than 0.15.
Therefore, it is preferable that plural types of ~C-reducing gas correlations of various
cases are obtained.
[0069]
The method of acquiring the ~C-reducing gas correlation will be described in
more detail. The blast furnace operation simulation is performed using various cases
where C/H in the reducing gas and the amount of the reducing gas blown are (the
amount thereof blown per ton of molten iron) are different from each other. The cases
also include the base operation (operation where the reducing gas volume is 0). Here,
it is preferable that the calculation conditions (operation conditions) are adjusted such
that the flame temperature and the molten iron temperature are as constant as possible in
the cases. In order to make the flame temperature constant, at least one of an blast
volume or an oxgen enrichment ratio in hot blast may be adjusted. In addition to or
instead of the adjustment of the above-described factors, at least one of the coke ratio
and the pulverized coal ratio may be adjusted. As a result, Input~C and the carbon
consumption in the reducing gas are acquired per case. Incidentally, a point
representing Input~C and the carbon consumption in the reducing gas of each of the
cases is plotted on, for example, the xy plane shown in FIG. 1. Points PI to P8 are
examples of the plotted points. Next, a fitted curve of each of the plots is acquired
using an approximation method such as a least -squares method. These fitted curves
form a graph showing the ~C-reducing gas correlation. The graphs Ll to L5 are
examples of the graph showing the ~C-reducing gas correlation.
[0070]
(2-2. Second Process)
In the second process, the carbon consumption in the reducing gas where
- 28 -
Input~C is a predetermined target value or higher is determined based on the ~Creducing
gas correlation acquired in the first process. That is, the ~C-reducing gas
correlation corresponding to C/H in reducing gas to be actually used is selected, and the
carbon consumption in the reducing gas where Input~C is a predetermined target value
or higher is determined based on the selected ~C-reducing gas correlation. C/H in the
reducing gas may be acquired, for example, by specifying the composition of the
reducing gas using the above-described measurement method and acquiring C/H based
on the specified composition of the reducing gas.
[0071]
Here, as described above, the ~C-reducing gas correlation is represented by the
upwardly convex graph. Accordingly, it is preferable that the carbon consumption in
the reducing gas is determined such that Input~C is close to the maximum value. As a
result, the reducing material ratio can be further reduced. For example, when C/H in
the reducing gas to be actually used is 0.15 or higher, it is preferable that the carbon
consumption in the reducing gas is determined in a range of 21 kg/t-pig to 107 kg/t-pig,
and it is more preferable that the carbon consumption in the reducing gas is determined
in a range of 21 kg/t-pig to 65 kg/t-pig. The reason for this is as described above.
That is, by determining the carbon consumption in the reducing gas in the range of 21
kg/t-pig to 107 kg/t-pig, Input~C can be made to be 4.0% or higher. Further, by
determining the carbon consumption in the reducing gas in the range of 21 kg/t-pig to
65 kg/t-pig, Input~C can be made to be high (specifically 4.0% or higher) with a
smaller amount of the reducing gas blown. Further, even when the carbon proportion
in the reducing gas is low (in particular, when the carbon proportion is lower than 0.6
kg/Nm3), the flame temperature can be stably maintained at the predetermined value or
higher while increasing Input~C.
- 29 -
[0072]
When the reducing gas in which C/H is 0.15 or higher is used and the carbon
consumption in the reducing gas is higher than 65 kg/t-pig, As described above, the
flame temperature tends to decrease. Therefore, it is preferable that operation elements
including the oxgen enrichment ratio are adjusted such that the flame temperature is a
predetermined value (for example, 2000°C) or higher. In addition, in the set value
range, Input~C decreases. Therefore, the carbon consumption in the reducing gas is
excessively high compared to the amount required for in-furnace reduction such that the
gas utilization factor decreases. Therefore, a countermeasure for improving the gas
utilization factor may be taken. For example, the iron-bearing material may be
changed to materials having excellent reducibility.
[0073]
(2-3. Third Process)
In the third process, the amount of the reducing gas blown into the blast
furnace (for example, the amount of the reducing gas blown per ton of molten iron) is
adjusted based on the carbon consumption in the reducing gas determined in the second
process and the carbon proportion in the reducing gas. For example, the amount of the
reducing gas blow can be obtained by dividing the carbon consumption in the reducing
gas by the carbon proportion in the reducing gas. By blowing the reducing gas into the
blast furnace in the determined amount thereof blown, the desired reducing material
ratio reduction effect can be obtained. The operation conditions other than the abovedescribed
conditions may be the same as those in the related art.
[0074]
Schematically, while alternately charging the iron-bearing materials and coke
in layers into the blast furnace from the top of the blast furnace, the reducing gas is
- 30 -
blown into the blast furnace together with the hot blast from the tuyere provided in the
blast furnace. The types of the iron-bearing materials and the coke are not particularly
limited, and iron-bearing materials and coke that are used in the blast furnace operation
in the related art can also be suitably used in the embodiment. The amount of the
reducing gas blown is set to the value determined in the third process. The reducing
gas may be, for example, one or more selected from the group consisting of COG,
natural gas, reformed top gas (BFG), and city gas. The reducing gas may be mixed gas
of the gases or hydrogen mixed gas obtained by mixing hydrogen gas with the gases
(including the mixed gas). In particular, the reducing gas in which C/H is lower than
0.15 may be produced by mixing hydrogen gas with COG or the like.
[0075]
The reducing gas may be blown into the blast furnace without being heated but
is preferably blown into the blast furnace after being heated. By blowing the reducing
gas into the blast furnace after being heated, further reduction in reducing material ratio
can be expected. The heating temperature is preferably about 300°C to 350°C.
[0076]
The tuyere for blowing the reducing gas into the blast furnace (hereinafter, also
referred to as "tuyere for reducing gas") is provided in, for example, a bosch part. The
tuyere for reducing gas may be provided in a shaft part. The tuyere for reducing gas
may be provided in both of the shaft part and the bosch part. The reducing gas blown
from the shaft part preferably includes a large amount of CO and/or H2 and is blown
while managing C/H.
[0077]
As in the blast furnace operation in the related art, the hot blast is blown into
the blast furnace. The temperature of the hot blast, the composition thereof, and the
- 31 -
amount thereof blown may be the same as those of the blast furnace operation in the
related art. For example, the hot blast includes air and may further include
hygroscopic moisture and enriched oxygen. The hot blast is blow into the blast
furnace, for example, from the tuyere provided in the bosch part. The tuyere for
blowing the hot blast into the blast furnace may be common to or different from the
tuyere for reducing gas.
[0078]
As described above, in the embodiment, the carbon consumption in the
reducing gas where Input~C is a predetermined target value or higher is determined
based on the ~C-reducing gas correlation acquired in advance, and the amount of the
reducing gas blown is determined based on the determined carbon consumption in the
reducing gas and the carbon proportion in the reducing gas. Accordingly, desired
Input~C can be realized relatively reliably. That is, the desired reducing material ratio
reduction effect can be obtained, and further the reducing material ratio can be reduced
more reliably. As a result, C02 emissions can be reduced. Further, according to the
~C-reducing gas correlation, when the carbon consumption in the reducing gas is a
given value (this value varies depending on C/H), Input~C shows a maximum value.
Accordingly, when the set value of the carbon consumption in the reducing gas is
determined such that Input~C is close to the maximum value, the reducing material
ratio can be further reduced. Further, by acquiring the correlation per C/H, the amount
of the reducing gas blown can be determined and managed based on the correlation
corresponding to C/H in the reducing gas. Accordingly, operation elements required
for increasing Input~C can be appropriately set and managed.
Examples
[0079]
- 32 -
Next, the effects of one aspect of the present invention will be described in
more detail using examples. However, conditions of the examples are merely
exemplary to confirm the operability and the effects of the present invention, and the
present invention is not limited to these condition examples. The present invention
can adopt various conditions within a range not departing from the scope of the present
invention as long as the object of the present invention can be achieved under the
conditions.
[0080]
<1. Example 1>
In Example 1, by performing the blast furnace operation simulation, it was
verified that, when C/H was 0.15 or higher, the ~C-reducing gas correlation was
present.
[0081]
In the blast furnace operation simulation, the above-described "blast furnace
mathematical model" was used. Calculation conditions are shown in Table 3. The
iron-bearing materials were all sintered ores. In addition, the composition of the
sintered ores was T-Fe: 58.5%, FeO: 7.5%, C/S: 1.9, and Ah03: 1.7%. In addition,
regarding coke, a case where coke having a composition of C: 87.2% and Ash: 12.6%
was used was assumed("%" represents "mass%" in all the cases).
- 33 -
[0082]
[Table 3]
Calculation Conditions
Productivity t/d/m3 2.71-2.81
Blast volume Nm3/t-pig 4-1035
Oxgen
enrichment % 7.6-78.9
ratio
Hygroscopic g/Nm3 5
Moisture of Air
Flame oc 2175-2225
temperature
[0083]
In Example 1, by performing the blast furnace operation simulation while
changing the type of the reducing gas (that is, the value of C/H) and the amount of the
reducing gas blown (the amount of the reducing gas blown per ton of molten iron), it
was verified that the ~C-reducing gas correlation was present. As the reducing gas,
the COG having the composition shown in Table 1 or the natural gas having the
composition shown in Table 2 was used. The reducing gas was blown into the blast
furnace from the tuyere provided in the bosch part. The blast volume and the oxgen
enrichment ratio in the hot blast were adjusted such that the flame temperature was as
constant as possible (that is, was a value in the range shown in Table 3) when the
reducing gas was blown. Note that the oxgen enrichment ratio was adjusted such that
the flame temperature was 2085 oc in Case 8 and the oxgen enrichment ratio was
adjusted such that the flame temperature was 2315°C in Case 9. Further, in all the
cases, the coke ratio was adjusted such that the molten iron temperature was constant.
As fixed conditions, the pulverized coal ratio was 115 kg/t-pig, and the blast
temperature was 1000°C. The calculation results are shown in Table 4 and FIG. 1.
- 34 -
[0084]
[Table 4]
Calculation Results
Type of Reducing gas Carbon
Consumption in Input~C Reducing Gas volume Reducing Gas
- Nm3/t-pig kg/t-pig %
Case 0 None 0 0 0.0
Case 1 COG 88 21 4.0
Case 2 COG 191 46 5.6
Case 3 COG 244 59 6.1
Case 4 Natural Gas 55 34 4.9
Case 5 Natural Gas 106 65 6.6
Case 6 Natural Gas 141 87 6.2
Case 7 Natural Gas 173 107 4.2
Case 8 COG 195 46 5.6
Case 9 COG 193 45 5.4
[0085]
As shown in Table 4 and FIG. 1, it was able to be verified that the ~C-reducing
gas correlation was present. Further, it was also verified that, when C/H in the
reducing gas was 0.15 or higher, the ~C-reducing gas correlation was uniquely
determined irrespective of the type of the reducing gas (in other words, irrespective of
C/H in the reducing gas). By determining the carbon consumption in the reducing gas
where Input~C is a predetermined target value or higher using the ~C-reducing gas
correlation and determining the amount of the reducing gas blown based on the
- 35 -
determined carbon consumption in the reducing gas, the reducing material ratio can be
reduced more reliably, and further C02 emissions can be reduced.
[0086]
<2. Example 2>
In Example 2, by performing the blast furnace operation simulation, it was
verified that, when C/H was lower than 0.15, the ~C-reducing gas correlation was
present.
[0087]
In the blast furnace operation simulation, the above-described "blast furnace
mathematical model" was used. Calculation conditions were the same as those of
Example 1. In addition, it was assumed that the same iron-bearing materials and the
same coke as those of Example 1 were used.
[0088]
In Example 2, by performing the blast furnace operation simulation while
changing C/H in the reducing gas and the amount of the reducing gas blown (the
amount of the reducing gas blown per ton of molten iron), it was verified that the ~Creducing
gas correlation was present. In the actual operation, C/H in the reducing gas
can be adjusted, for example, by mixing the COG having the composition shown in
Table 1 with hydrogen gas at a different mixing ratio per case. The reducing gas was
blown into the blast furnace from the tuyere provided in the bosch part. The blast
volume and the oxgen enrichment ratio in the hot blast were adjusted such that the
flame temperature was as constant as possible (that is, was a value in the range shown in
Table 3) when the reducing gas was blown. Further, in all the cases, the coke ratio
was adjusted such that the molten iron temperature was constant. As fixed conditions,
the pulverized coal ratio was 115 kg/t-pig, and the blast temperature was 1000°C. The
- 36 -
calculation results are shown in Table 5 and FIG. 1.
- 37 -
[0089]
[Table 5]
Calculation Results
Carbon
C/Hin Reducing gas Consumption
Input~C Reducing Gas volume in Reducing
Gas
- Nm3/t-pig kg/t-pig %
Case 0 - 0 0 0.0
Case 1 0.054 99 6.1 5.7
Case 2 0.054 199 12.1 10.0
Case 3 0.054 294 17.9 11.8
Case 4 0.054 396 24.1 11.9
Case 5 0.097 99 11.1 5.6
Case 6 0.097 199 22.5 8.3
Case 7 0.097 292 33.0 10.2
Case 8 0.097 393 44.4 9.9
Case 9 0.137 98 16.1 4.2
Case 10 0.137 199 32.9 8.0
Case 11 0.137 293 48.4 9.2
Case 12 0.137 340 56.1 9.0
Case 13 0.02 99 2.6 5.1
Case 14 0.02 390 10.2 13.7
Case 15 0.02 473 12.3 13.4
[0090]
- 38 -
As shown in Table 5 and FIG. 1, it was able to be verified that the ~C-reducing
gas correlation was present. Further, it was also verified that, when C/H in the
reducing gas was lower than 0.15, the ~C-reducing gas correlation varied depending on
C/H in the reducing gas. Accordingly, the correlation corresponding to CIH in the
reducing gas is selected, and the carbon consumption in the reducing gas where
Input~C is a predetermined target value or higher is determined using the selected
correlation. By determining the amount of the reducing gas blown based on the
determined carbon consumption in the reducing gas, the reducing material ratio can be
reduced more reliably, and further C02 emissions can be reduced.

WE CLAIMS

1. A blast furnace operation method in which reducing gas including
hydrogen atoms and carbon atoms is blown into a blast furnace, the method comprising:
acquiring a correlation between a carbon consumption in the reducing gas and
a reduction Input~C in specific carbon consumption caused by blowing the reducing
gas into the blast furnace per molar ratio C/H of carbon atoms to hydrogen atoms in the
reducing gas;
determining a carbon consumption in the reducing gas where the reduction
Input~C in specific carbon consumption is a predetermined target value or higher on the
basis of the correlation acquired per C/H; and
adjusting an amount of the reducing gas blown into the blast furnace on the
basis of the determined carbon consumption in the reducing gas and a carbon proportion
in the reducing gas.
2. The blast furnace operation method according to claim 1,
wherein the molar ratio C/H of the carbon atoms to the hydrogen atoms in the
reducing gas is 0.15 or higher.
3. The blast furnace operation method according to claim 2,
wherein the correlation is represented by a quadratic expression of the carbon
consumption in the reducing gas.
4. The blast furnace operation method according to claim 3,
wherein the correlation is represented by Y = a1X2 + b1X + c1 (where X
represents the carbon consumption in the reducing gas, Y represents the reduction
Input~C in specific carbon consumption, and all the coefficients a1, b1, and c1
represent values that do not depend on the molar ratio C/H).
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5. The blast furnace operation method according to claim 4,
wherein the carbon consumption in the reducing gas is determined in a range of
21 kg/t-pig to 107 kg/t-pig.
6. The blast furnace operation method according to claim 4 or 5,
wherein the carbon consumption in the reducing gas is determined in a range of
21 kg/t-pig to 65 kg/t-pig.
7. The blast furnace operation method according to claim 1,
wherein the molar ratio C/H of the carbon atoms to the hydrogen atoms in the
reducing gas is higher than 0 and lower than 0.15.
8. The blast furnace operation method according to claim 7,
wherein the molar ratio C/H of the carbon atoms to the hydrogen atoms in the
reducing gas is 0.13 or lower.
9. The blast furnace operation method according to claim 7 or 8,
wherein the molar ratio C/H of the carbon atoms to the hydrogen atoms in the
reducing gas is 0.10 or lower.
10. The blast furnace operation method according to any one of claims 7 to 9,
wherein the correlation is represented by Y = a2X2 + b2X + c2 (where X
represents the carbon consumption in the reducing gas, Y represents the reduction
Input~C in specific carbon consumption, and at least one of the coefficients a2, b2, and
c2 represents a function including the molar ratio C/H as a variable).
11. The blast furnace operation method according to any one of claims 1 to
10,
wherein when the reducing gas is blown into the blast furnace, a flame
temperature is adjusted to be 2000°C or higher.
12. The blast furnace operation method according to claim 11,
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wherein in order to adjust the flame temperature to be 2000°C or higher, at
least one of an blast volume or an oxgen enrichment ratio in hot blast is adjusted.
13. The blast furnace operation method according to any one of claims 1 to
12,
wherein the reducing gas is selected from the group consisting of coke oven
gas, natural gas, reformed top gas (BFG), city gas, mixed gas thereof, and hydrogen
mixed gas obtained by mixing hydrogen gas therewith.