Note: Descriptions are shown in the official language in which they were submitted.
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[Document Type] Specification
[Title of the _Invention] BLAST FURNACE OPERATION METHOD
[Technical Field of the Invention]
[0001]
The present invention relates to a blast furnace operation method.
Priority is claimed on Japanese Patent Application No. 2019-216568, filed in
Japan on November 29, 2019 and Japanese Patent Application No. 2020-092467,
filed
in Japan on May 27, 2020, the contents of which are incorporated herein by
reference.
[Related Art]
[0002]
In the steel industry, a blast furnace method is a mainstream 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 in the
blast furnace
from the top of the blast furnace, and hot blast is blown into the blast
furnace from a
tuyere of a lower part of the blast furnace. The hot blast reacts with
pulverized coal
blown together with the hot blast and the coke in the blast furnace such that
a 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 materials
while
heating the iron-bearing 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
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extracted from a tap hole and is provided for the next steelmaking process.
Accordingly, in the blast furnace method, a carbon material such as coke or
pulverized
coal is used as a reducing material.
[0003]
Meanwhile, in recent years, the prevention of global warming has been called
for, and the reduction of carbon dioxide (CO2 gas) emissions, which is one
greenhouse
gas, has become a social problem. As described above, in the blast furnace
method, a
carbon material is used as a reducing material. Thus, a large amount of CO2
gas is
generated. Accordingly, the steel industry is one of the main industries
producing CO2
gas emissions and needs to meet the demands of society. Specifically, further
reduction in a reducing material ratio (the amount of a reducing material used
per ton of
molten iron) is urgently required in the blast furnace operation.
[0004]
The reducing material has a function of heating charges inside the furnace as
a
heat source and a function of reducing the iron-bearing material in the
furnace, and the
reduction efficiency in the furnace needs to be increased in order to reduce
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 endothermic heat. Accordingly, in order to reduce the
reducing
material ratio, it is important to suppress the occurrence of this reaction as
much as
possible. The direct reduction reaction occurs in a lower part of the blast
furnace.
Therefore, as long as the iron-bearing materials can be sufficiently reduced
by a
reducing gas such as CO or H2 before the iron-bearing materials reach the
furnace lower
part, the iron-bearing materials that are a target of the direct reduction
reaction can be
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reduced.
[0005]
As the related art for solving the above-described problems, for example, as
disclosed in Patent Documents 1 to 6, a technique of blowing a reducing gas (1-
12 gas,
coke oven gas (COG), natural gas, city gas, or the like) together with hot
blast from a
tuyere to improve the reducing gas potential in the furnace is known. in a
case where
the reducing gas is a carbon-containing reducing gas (a reducing gas in which
carbon
atoms are contained in a molecular structure of the gas, for example, a
hydrocarbon
gas), the carbon atoms in the carbon-containing gas become CO gas in the blast
furnace,
which reduces the iron-bearing materials. In a case where the reducing gas is
hydrogen gas (H2 gas), the hydrogen gas reduces the iron-bearing materials.
Accordingly, the amount of the iron-bearing materials that are a target for
the direct
reduction reaction can be reduced. In addition, in the following description,
unless
particularly specified, "carbon" and "hydrogen" mean "carbon atom" and
"hydrogen
atom", respectively.
[Prior Art Document]
[Patent Document]
[0006]
[Patent Document 1] Japanese Patent No. 6019893
[Patent Document 21 Japanese Patent No. 5987773
[Patent Document 3] Japanese Patent No. 5050706
[Patent Document 4] Japanese Patent No. 5770124
[Patent Document 51 Japanese Patent No. 5315732
[Patent Document 6] Japanese Patent No. 5851828
[Disclosure of the invention]
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[Problems to be Solved by the invention]
[0007]
However, in the techniques disclosed in Patent Documents 1 to 6, the reducing
gas volume blown from the tuyere is small, and the effect of reducing the CO2
emissions is small.
[0008]
Thus, the present invention has been made in view of the above problems, and
an object of the present invention is to provide a new and improved blast
furnace
operation method capable of increasing the gas volume of a high-concentration
hydrogen-containing gas blown from a tuyere as a reducing gas while
maintaining a
stable blast furnace operation, and further reducing the CO2 emissions.
[Means for Solving the Problem]
[0009]
In order to solve the above problems, according to a certain viewpoint of the
present invention, there is provided a blast furnace operation method
comprising
blowing a high-concentration hydrogen-containing gas containing 80 mol% or
more of
hydrogen gas from a tuyere under: a condition in which a blowing temperature
of the
high-concentration hydrogen-containing gas is room temperature or higher and
300 C
or lower and a gas volume of the hydrogen gas in the high-concentration
hydrogen-
containing gas is 200 Nm3/t or more and 500 Nm3/t or less; a condition in
which the
blowing temperature of the high-concentration hydrogen-containing gas is
higher than
300 C and 600 C or lower and the gas volume of the hydrogen gas in the high-
concentration hydrogen-containing gas is 145 Nm3/t or more; a condition in
which the
blowing temperature of the high-concentration hydrogen-containing gas is
higher than
600 C and 900 C or lower and the gas volume of the high-concentration hydrogen-
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containing gas is 125 Nm3/t or more; a condition in which the blowing
temperature of
the high-concentration hydrogen-containing gas is higher than 900 C and 1200 C
or
lower and the gas volume of the hydrogen gas in the high-concentration
hydrogen-
containing gas is 110 Nm3/t or more; or a condition in which the blowing
temperature of
the high-concentration hydrogen-containing gas is higher than 1200 C and the
gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
is 100
Nm3/t or more.
[0010]
Here, the blowing temperature of the high-concentration hydrogen-containing
gas may be room temperature or higher and 300 C or lower and the gas volume of
the
hydrogen gas in the high-concentration hydrogen-containing gas may be 200
Nm3/t or
more and 300 Nm3/t or less.
[0011]
Here, the blowing temperature of the high-concentration hydrogen-containing
gas may be higher than 300 C and 600 C or lower and the gas volume of the
hydrogen
gas in the high-concentration hydrogen-containing gas may be 145 Nm3/t or more
and
600 Nm3/t or less.
[0012]
Additionally, the flame temperature may be 2050 C or lower.
[0013]
Additionally, the flame temperature may be set to higher than 2050 C and
2150 C or lower.
[0014]
Additionally, the flame temperature may be set to higher than 2150 C and
2250 C or lower.
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[0015]
Additionally, the blowing temperature of the high-concentration hydrogen-
containing gas may be higher than 600 C and 1400 C or lower.
[0016]
Additionally, in a case where the blowing temperature of the high-
concentration hydrogen-containing gas is higher than 600 C, the gas volume of
the
hydrogen gas in the high-concentration hydrogen-containing gas may be 1000
Nm3/t or
less.
[0017]
Additionally, in a case where the blowing temperature of the high-
concentration hydrogen-containing gas is higher than 600 C and the gas volume
of the
hydrogen gas in the high-concentration hydrogen-containing gas is 400 Nm3/t or
more,
a flame temperature may be set to 2050 C or lower.
[0018]
According to another aspect of the present invention, there is provided a
blast
furnace operation method comprising obtaining a gas volume-carbon consumption
parameter correlation, which is a correlation between a gas volume of hydrogen
gas in a
high-concentration hydrogen-containing gas and a carbon consumption parameter
related to a carbon consumption amount when a blowing temperature of the high-
concentration hydrogen-containing gas containing 80 mol% or more of the
hydrogen
gas is a predetermined value, in advance for each flame temperature;
determining the
gas volume of the hydrogen gas in the high-concentration hydrogen-containing
gas at
which the carbon consumption amount is reduced compared to that of a current
operation. on the basis of the gas volume-carbon consumption parameter
correlation;
and blowing the high-concentration hydrogen-containing gas from the tuyere at
the
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determined gas volume.
[0019]
Additionally, the correlation between the hydrogen gas volume into the high-
concentration hydrogen-containing gas and the carbon consumption parameter may
be
obtained for each blowing temperature of the high-concentration hydrogen-
containing
gas.
[0020]
Additionally, a gas volume-pressure drop change correlation, which is a
correlation between the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas and a change amount of a pressure loss with respect to
a base
operation when the blowing temperature of the high-concentration hydrogen-
containing
gas is a predetermined value. may be obtained in advance for each flame
temperature,
and the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing
gas at which the carbon consumption amount is reduced compared to that of the
current
operation and the change amount of the pressure loss is a value within a
predetermined
range may be determined on the basis of the gas volume-carbon consumption
parameter
correlation and the gas volume-pressure drop change correlation.
[0021]
Additionally, a gas volume-top gas temperature change amount correlation,
which is a correlation between the gas volume of the hydrogen gas in the high-
concentration hydrogen-containing gas and a change amount of a top gas
temperature
with respect to a base operation when the blowing temperature of the high-
concentration
hydrogen-containing gas is a predetermined value, may be obtained in advance
for each
flame temperature, and the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas at which the carbon consumption amount is reduced
compared
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to that of the current operation and the change amount of the top gas
temperature is a
value within a predetermined range may be determined on the basis of the gas
volume-
carbon consumption parameter correlation and the gas volume-top gas
temperature
change amount correlation.
[Effects of the Invention]
[0022]
As described above, according to the above viewpoint of the present invention,
it is possible to increase the gas volume of the high-concentration hydrogen-
containing
gas blown from the tuyere as a reducing gas while maintaining a stable blast
furnace
operation, and further reduce the CO2 emissions.
[Brief Description of the Drawings]
[0023]
FIG. I is a diagram for explaining a blowing temperature of a high-
concentration hydrogen-containing gas.
FIG. 2 is a graph showing the correlation between the gas volume of pure
hydrogen gas at room temperature and the reduction percentage Input AC of
specific
carbon consumption for each flame temperature Tf.
FIG. 3 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at 300 C and the reduction percentage Input AC of the specific
carbon
consumption for each flame temperature Tf.
FIG. 4 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at 350 C and the reduction percentage Input AC of the specific
carbon
consumption.
FIG. 5 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at 600 C and the reduction percentage Input AC of the specific
carbon
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consumption for each flame temperature Tf.
FIG. 6 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at 650 C and the reduction percentage Input AC of the specific
carbon
consumption.
FIG. 7 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at 900 C and the reduction percentage Input AC of the specific
carbon
consumption for each flame temperature Tf.
FIG. 8 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at 950 C and the reduction percentage Input AC of the specific
carbon
consumption.
FIG. 9 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at 1200 C and the reduction percentage Input AC of the specific
carbon
consumption for each flame temperature Tf.
FIG. 10 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at 1250 C and the reduction percentage Input AC of the specific
carbon
consumption.
FIG. 11 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at room temperature or the gas volume of the hydrogen gas in an
80 mol%
H2-20 mol% N2 high-concentration hydrogen-containing gas at room temperature
and
the reduction percentage Input AC of the specific carbon consumption.
FIG. 12 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at room temperature and the change amount of pressure loss for
each
flame temperature Tf.
FIG. 13 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at room temperature and the change amount of a top gas
temperature for
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each flame temperature Tf.
FIG. 14 is a graph showing the correlation between the gas volume of the pure
hydrogen gas at 1200 C and the change amount of pressure loss when the flame
temperature Tf reaches 2100 C.
FIG. 15 is a graph showing the correlation between the blowing temperature of
the pure hydrogen gas and the gas volume of pure hydrogen gas required to set
the
reduction percentage Input AC of specific carbon consumption to 10%.
FIG. 16 is a graph showing the correlation between the blowing temperature of
the pure hydrogen gas and the gas volume of pure hydrogen gas required to set
the
reduction percentage Input AC of the specific carbon consumption to 20%.
[Embodiments of the Invention]
[0024]
Preferred embodiments of the present invention will be described in detail
below with reference to the accompanying drawings. In addition, in the present
embodiment, a numerical range represented using "to" is a range including
numerical
values described before and after "to" as a lower limit and an upper limit.
Additionally, the "reducing material ratio" is the total mass of a reducing
material
required to produce 1 ton of molten iron. Therefore, the reducing material
ratio is
basically the total mass of the coke and the pulverized coal required to
produce 1 ton of
molten iron, and the mass of a carbon-containing reducing gas in a high-
concentration
hydrogen-containing gas is treated as not included in the reducing material
ratio.
Additionally, the "specific carbon consumption (Input C)" is the carbon
required to
produce 1 ton of molten iron (that is, the carbon consumption amount per ton
of molten
iron). The "reduction percentage Input AC of specific carbon consumption" is
the
reduction percentage of specific carbon consumption to the base operation that
is an
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operation in which the high-concentration hydrogen-containing gas is not
blown.
Assuming that the Input C of the base operation in units of kg/t is A and the
Input C at
the time of the operation in units of kg/t is B, the Input AC is expressed by
the following
formula.
Input AC = (A-B)/A x 100 (%)
The larger the reduction percentage Input AC of the specific carbon
consumption, the smaller the reducing material ratio, and the more CO2
emissions are
reduced.
[0025]
<1. Findings by the present inventor>
In order to solve the above problems, the present inventor has focused on the
high-concentration hydrogen-containing gas as a reducing gas. Here, the high-
concentration hydrogen-containing gas in the present embodiment is a gas
containing 80
mol% or more of hydrogen gas (mol% of hydrogen gas with respect to the total
amount
of substances of all the gases constituting the high-concentration hydrogen-
containing
gas). The high-concentration hydrogen-containing gas may be pure hydrogen gas
(gas
having a hydrogen gas concentration of 100 mol%).
[0026]
Further, the present inventors have focused on the gas volume of the hydrogen
gas in the high-concentration hydrogen-containing gas (hereinafter, also
simply referred
to as the gas volume of hydrogen) and the blowing temperature of the high-
concentration hydrogen-containing gas. The reduction reaction of an iron-
bearing
material by the hydrogen gas in the high-concentration hydrogen-containing gas
is an
endothermic reaction. In order to compensate for a temperature drop caused by
the
endothermic reaction, raising the blowing temperature of the hydrogen gas can
be
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considered. However, it is extremely difficult to find the amount of drop in
the
temperature inside the furnace in a case where a large amount of the hydrogen
gas in the
high-concentration hydrogen-containing gas is blown in, and the degree of heat
compensation required depending on the amount of decrease in the temperature
inside
the furnace. Therefore, detailed study of these has not been performed so far.
The
present inventors first performed a detailed study on the above matters.
Specifically,
finding the composition of various gases such as hydrogen gas and CO gas in
the high-
concentration hydrogen-containing gas and the reduction reaction rate of the
high-
concentration hydrogen-containing gas at various blowing temperatures, finding
the
effect of the temperature inside the furnace, which changes due to the
reduction reaction
heat of these gases, on the reduction reaction rate and the effect of the gas
composition,
which changes due to the reduction reaction, on the reduction reaction rate,
and then
finding the amounts of heat such that the reduction reaction rate does not
decrease were
performed for the entire furnace. For such a study, performance of multiple
tests on an
actual blast furnace machine, tests using an experimental device that can blow
the gas
inside the blast furnace under the conditions inside the blast furnace while
simulating
adiabatic conditions using a test blast furnace level device, and study
performed by a
simulation model are needed. The present inventors performed the above study
using
the simulation model, and as a result, found that an appropriate range of the
gas volume
is present for each blowing temperature.
That is, in a case where the blowing temperature of the high-concentration
hydrogen-containing gas is 600 C or lower, the reduction percentage Input AC
of the
specific carbon consumption does not simply increase with an increase in the
gas
volume of hydrogen gas in the high-concentration hydrogen-containing gas, but
is
relaxed and starts to decrease when the gas volume increases to some extent.
Also, the
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gas volume of the hydrogen gas in the high-concentration hydrogen-containing
gas
when the reduction percentage Input AC of the specific carbon consumption is
relaxed
and starts to decrease varies depending on the blowing temperature of the high-
concentration hydrogen-containing gas. On the other hand, in a case where the
blowing temperature of the high-concentration hydrogen-containing gas is
higher than
600 C, the reduction percentage Input AC of the specific carbon consumption
tends to
increase with an increase in the gas volume. When the gas volume of the
hydrogen
gas in the high-concentration hydrogen-containing gas increases to sonic
extent, the
reduction percentage Input AC of the specific carbon consumption becomes, for
example, 7% or more. Therefore, the CO2 emissions can be significantly reduced
by
blowing the gas volume of the high-concentration hydrogen-containing gas in
the blast
furnace, which is determined according to the gas volume of hydrogen gas in
this
appropriate range. For example, as shown in examples described below, the
reduction
percentage Input AC of specific carbon consumption during the operation of the
blast
furnace can be set to 7% or more, and the CO2 emissions can be significantly
reduced.
The present inventors came up with a blast furnace operation method according
to the
present embodiment on the basis of such knowledge. Hereinafter, the present
embodiment will be described in detail.
[0027]
<2. Composition of high-concentration hydrogen-containing gas>
In the blast furnace operation method according to the present embodiment, the
high-concentration hydrogen-containing gas is blown from a tuyere. Thus,
first, the
composition of the high-concentration hydrogen-containing gas will be
described. The
high-concentration hydrogen-containing gas is a gas containing 80 mol% or more
of
hydrogen gas as described above. The high-concentration hydrogen-containing
gas
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includes pure hydrogen gas. The high-concentration hydrogen-containing gas
includes
gas components other than the hydrogen gas, for example, the above-described
carbon-
containing reducing gas (for example, a hydrocarbon gas), CO gas, CO2 gas, H20
gas,
N2 gas, or the like. However, the total concentration of the other gases is
less than 20
mol%. [0028]
Gases of which the total concentration of the other gas components is 20 mol%
or more are not included in the high-concentration hydrogen-containing gas in
the
present embodiment. This is because the reduced amount of CO2 gas decreases
significantly in a case where the concentration of the other gases is 20 mol%
or more.
For example, since hydrocarbon gases. CO2 gas, and H20 gas among other gas
components cause an endothermic reaction when the gases are decomposed at a
tuyere
tip, the reduction efficiency in the blast furnace decreases. For this reason,
the amount
of iron-bearing materials that reach a lower part of the blast furnace without
being
reduced increases. Therefore, the amount of direct reduction reaction by coke
increases. Therefore, a large amount of the reducing material is required to
maintain
the temperature in the blast furnace, and the amount of CO2 gas reduction
decreases
significantly. For example, in a case where COG (coke furnace gas) containing
50
mol% of hydrogen gas is blown into the blast furnace with a gas volume of 600
Nm3/t,
the hydrogen gas is blown into the blast furnace with a gas volume of 300
Nm3/t. The
effect of reducing the CO2 emissions in this case is significantly inferior to
that when
the pure hydrogen gas is blown into the blast furnace with a gas volume of 300
Nm3/t,
and does not lead to a drastic reduction of the CO2 emissions (for example,
reduction
percentage Input AC of specific carbon consumption > 7%). In addition, as
shown in
the examples described below, in the example of the pure hydrogen gas at room
temperature, the effect of reducing the CO2 emissions is maximized when the
gas
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volume is about 300 Nm3/t.
[0029]
<3. Blast furnace operation method>
Next, the blast furnace operation method according to the present embodiment
will be described. In the blast furnace operation method according to the
present
embodiment, first, the blowing temperature of the high-concentration hydrogen-
containing gas is determined within a range of room temperature or higher.
[0030]
Here, the blowing temperature of the high-concentration hydrogen-containing
gas (hereinafter, this may be simply referred to as "blowing temperature")
will be
described with reference to FIG. 1. FIG. 1 is a diagram for explaining the
blowing
temperature. The temperature of the high-concentration hydrogen-containing gas
is
regulated, for example, in a gas tank 3 including a heater 5. That is, the
high-
concentration hydrogen-containing gas is sent to the tuyere 2 for blowing hot
blast
provided at the lower part of the blast furnace 1 after being heated by the
heater 5 in the
gas tank 3 or while remaining unheated at room temperature. The high-
concentration
hydrogen-containing gas sent to the tuyere 2 can be blown into the blast
furnace 1 from
the tuyere 2. Specifically, the high-concentration hydrogen-containing gas
sent to the
tuyere 2 is mixed (merged) with the hot blast generated in a hot blast furnace
4 and then
blown into the blast furnace 1 from the tuyere 2. The blowing temperature is
the
temperature of the high-concentration hydrogen-containing gas immediately
before
being mixed with the hot blast when the hot blast is blown into the blast
furnace I from
the tuyere 2. In actual operation (actual furnace), for example, since there
is no
temperature drop from the heater 5 that heats the high-concentration hydrogen-
containing gas until the gas is blown into the blast furnace 1, the set
temperature of the
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heater 5 can be set as the blowing temperature. Although the temperature of
the high-
concentration hydrogen-containing gas rises due to the mixing of the hot blast
and the
high-concentration hydrogen-containing gas, the temperature in this case is
not the
blowing temperature in the present embodiment. Additionally, although the
blast
temperature is described in Patent Document 1, the blast temperature in Patent
Document 1 is different from the blowing temperature in the present
embodiment.
[0031]
As shown in the examples described below, the CO2 emissions can be
significantly reduced even in a case where the high-concentration hydrogen-
containing
gas is blown from the tuyere at room temperature without heating (see FIG. 2).
FIG. 2
is a graph showing the correlation between the gas volume of the pure hydrogen
gas at
room temperature and the reduction percentage Input AC of the specific carbon
consumption for each flame temperature Tf. This graph is obtained by blast
furnace
operation simulation. Details of the blast furnace operation simulation are
described in
the examples. However, here, 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, pp.
15 to 22 was
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 simulation conditions were the same as in the examples
described
below. As shown in FIG. 2, in a case where the gas volume of the pure hydrogen
gas
at room temperature is 200 to 500 Nm3/t, it is possible to set the reduction
percentage
Input AC of the specific carbon consumption to, for example, 7% or more. The
reduction percentage Input AC of the specific carbon consumption is preferably
8% or
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more. In addition, "room temperature" in the present embodiment means an
unheated
state, and specifically, is a temperature of 5 C or higher and 35 C or lower.
[0032]
Although details will be described below, when the blowing temperature is
within a range of room temperature or higher, the reduction percentage Input
AC of the
specific carbon consumption to the same gas volume increases as the blowing
temperature of the high-concentration hydrogen-containing gas is higher (see
FIGS. 2 to
10). FIG. 3 is a graph showing the correlation between the gas volume of the
pure
hydrogen gas at 300 C and the reduction percentage Input AC of the specific
carbon
consumption for each flame temperature Tf. FIG. 4 is a graph showing the
correlation
between the gas volume of the pure hydrogen gas at 350 C and the reduction
percentage
Input AC of the specific carbon consumption. FIG. 5 is a graph showing the
correlation between the gas volume of the pure hydrogen gas at 600 C and the
reduction
percentage Input AC of the specific carbon consumption for each flame
temperature Tf.
FIG. 6 is a graph showing the correlation between the gas volume of the pure
hydrogen
gas at 650 C and the reduction percentage Input AC of the specific carbon
consumption.
FIG. 7 is a graph showing the correlation between the gas volume of the pure
hydrogen
gas at 900 C and the reduction percentage Input AC of the specific carbon
consumption
for each flame temperature Tf. FIG. 8 is a graph showing the correlation
between the
gas volume of the pure hydrogen gas at 950 C and the reduction percentage
Input AC of
the specific carbon consumption. FIG. 9 is a graph showing the correlation
between
the gas volume of the pure hydrogen gas at 1200 C and the reduction percentage
Input
AC of specific carbon consumption for each flame temperature Tf. FIG. 10 is a
graph
showing the correlation between the gas volume of the pure hydrogen gas at
1250 C
and the reduction percentage Input AC of the specific carbon consumption.
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[0033]
These graphs are obtained from the above-described blast furnace operation
simulation. The details will be described in the examples. It can be seen that
the
reduction percentage Input AC of specific carbon consumption of FIGS. 3 to 10
is
higher than the reduction percentage Input AC of the specific carbon
consumption of
FIG. 2. The higher the blowing temperature of the high-concentration hydrogen-
containing gas, the higher the sensible heat of a Bosch gas (a mixed gas of
nitrogen gas,
hydrogen gas, and CO gas) generated in the blast furnace. Thus, it is
considered that
more reducing gas will reduce iron-bearing materials. That is, the reduction
efficiency
will become higher. For this reason, it is considered that a higher blowing
temperature
of the high-concentration hydrogen-containing gas will lead to a larger
reduction
percentage Input AC of the specific carbon consumption. Therefore, from the
viewpoint of increasing the reduction percentage Input AC of the specific
carbon
consumption, it is preferable to raise the blowing temperature of the high-
concentration
hydrogen-containing gas. Specifically, it is preferable to determine the
blowing
temperature in a range of higher than 300 C, more preferably in a range of
higher than
600 C, and more preferably in a range of higher than 900 C.
[0034]
However, in order to raise the blowing temperature of the high-concentration
hydrogen-containing gas to higher than 600 C, there is a case where large-
scale
equipment remodeling is required. For this reason, in a case where it is
difficult to set
the blowing temperature of the high-concentration hydrogen-containing gas to
higher
than 600 C with existing equipment, the blowing temperature of the high-
concentration
hydrogen-containing gas may be determined within a range of room temperature
to
600 C. On the other hand, in a case where the blowing temperature of the high-
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CA 03161120 2022-05-10
concentration hydrogen-containing gas can be increased to higher than 600 C
with the
existing equipment (or by remodeling the existing equipment), the blowing
temperature
of the high-concentration hydrogen-containing gas may be determined within a
range of
higher than 600 C.
[0035]
Next, the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing gas is determined. Here, the gas volume of the hydrogen gas in the
high-
concentration hydrogen-containing gas is the flow rate per ton of molten iron
of
hydrogen gas in the high-concentration hydrogen-containing gas blown into the
blast
furnace from the tuyere, and the unit is Nm3/t. When the high-concentration
hydrogen-containing gas is the pure hydrogen gas, the gas volume of the
hydrogen gas
in the high-concentration hydrogen-containing gas is equal to the gas volume
of the
high-concentration hydrogen-containing gas. When the high-concentration
hydrogen-
containing gas is a mixed gas containing gases other than the hydrogen gas,
the gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
is the
amount obtained by multiplying the gas volume of the high-concentration
hydrogen-
containing gas in units of mol% by the ratio of the hydrogen gas. In the
actual
operation, the gas volume of the hydrogen gas in the high-concentration
hydrogen-
containing gas is calculated from the value indicated by a flow meter provided
at a
discharge port of a high-concentration hydrogen-containing gas supply source
(for
example, a gas tank) and the ratio of the hydrogen gas in the high-
concentration
hydrogen-containing gas in units of mol%.
[0036]
In the present embodiment, the gas volume is determined by classifying cases
at the blowing temperature of the high-concentration hydrogen-containing gas.
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CA 03161120 2022-05-10
Specifically, in a case where the blowing temperature is room temperature to
300 C, the
gas volume of the hydrogen gas in the high-concentration hydrogen-containing
gas is
determined within a range of 200 to 500 Nm3/t. On the other hand, in a case
where the
blowing temperature is higher than 300 C and 600 C or lower, the gas volume of
the
hydrogen gas in the high-concentration hydrogen-containing gas is determined
within a
range of 145 Nni3/t or more. In a case where the blowing temperature of the
high-
concentration hydrogen-containing gas is higher than 600 C and 900 C or lower,
the
gas volume of the high-concentration hydrogen-containing gas is determined
within a
range of 125 Nm3/t or more. In a case where the blowing temperature of the
high-
concentration hydrogen-containing gas is higher than 900 C and 1200 C or
lower, the
gas volume of the hydrogen gas in the high-concentration hydrogen-containing
gas is
determined within a range of 110 Nm3/t or more. In a case where the blowing
temperature of the high-concentration hydrogen-containing gas is higher than
1200 C,
the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing gas
is determined within a range of 100 Nm3/t or more.
[0037]
The reason why cases are classified according to the blowing temperature in
this way is that a preferred gas volume varies slightly depending on the
blowing
temperature. In addition, in the following description, a case where the high-
concentration hydrogen-containing gas is the pure hydrogen gas will be
described as an
example. However, as shown in Example 1-2 described below, even in a case
where
the high-concentration hydrogen-containing gas contains a gas component other
than
the hydrogen gas, the correlation between the blowing temperature of the high-
concentration hydrogen-containing gas and the preferred gas volume does not
change.
[0038]
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CA 03161120 2022-05-10
As shown in FIGS. 2 and 3, in a case where the blowing temperature of the
high-concentration hydrogen-containing gas is from room temperature to 300 C,
the
reduction percentage Input AC of the specific carbon consumption increases
when the
gas volume of the hydrogen gas in the high-concentration hydrogen-containing
gas is
increased from 0 in the base operation. Then, when the gas volume of the
hydrogen
gas in the high-concentration hydrogen-containing gas reaches about 300 Nm3/t,
the
reduction percentage Input AC of the specific carbon consumption reaches a
peak, and
when the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing gas further increases, the reduction percentage Input AC of the
specific
carbon consumption starts to decrease. Then, in a case where the gas volume of
the
hydrogen gas in the high-concentration hydrogen-containing gas is in a range
of 200 to
500 Nm3/t, it is possible to set the reduction percentage Input AC of the
specific carbon
consumption to 7% or more. In addition, in a case where the high-concentration
hydrogen-containing gas is pure hydrogen gas, the gas volume of the hydrogen
gas in
the high-concentration hydrogen-containing gas is the gas volume of the high-
concentration hydrogen-containing gas. However, in a case where the high-
concentration hydrogen-containing gas includes a gas component other than the
hydrogen gas, this value is the amount obtained by multiplying the gas volume
of the
high-concentration hydrogen-containing gas by the ratio of the hydrogen gas
(mol%).
[0039]
The reduction reaction of the iron-bearing materials with the hydrogen gas
(that is, the hydrogen reduction reaction) is an endothermic reaction. For
this reason,
in a case where the gas volume of the hydrogen gas in the high-concentration
hydrogen-
containing gas exceeds 300 Nm3/t, it is considered that such an endothermic
reaction
occurs frequently in the furnace and the temperature inside the furnace drops.
Also,
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CA 03161120 2022-05-10
such a decrease in the temperature inside the furnace is considered to reduce
the
reduction efficiency of the reducing gas containing hydrogen gas. In order to
prevent
such a decrease in reduction efficiency, it is necessary to increase the
reducing material
ratio to perform the operation. For this reason, in a case where the gas
volume of the
hydrogen gas in the high-concentration hydrogen-containing gas exceeds 300
Nm3/t, the
reduction percentage Input AC of the specific carbon consumption starts to
decrease.
Therefore, in a case where the blowing temperature is room temperature to 300
C, it is
preferable to determine the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas within a range of 200 to 400 Nm3/t, and it is more
preferable
to determine the gas volume within a range of 200 to 300 Nm3/t. In this case,
it is
possible to set the reduction percentage Input AC of the specific carbon
consumption to
8% or more.
[0040]
As shown in FIGS. 4 and 5, even in a case where the blowing temperature of
the high-concentration hydrogen-containing gas is higher than 300 C and 600 C
or
lower, the reduction percentage Input AC of the specific carbon consumption
increases
when the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing gas is increased from 0 Nm3/t Nm in the base operation. Then, when
the
gas volume of the hydrogen gas in the high-concentration hydrogen-containing
gas is
145 Nm3/t or more, the reduction percentage Input AC of the specific carbon
consumption becomes 7% or more. In a case where the blowing temperature of the
high-concentration hydrogen-containing gas is 600 C, as shown in FIG. 5, the
gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
is about
600 Nm3/t, and the reduction percentage Input AC of the specific carbon
consumption
reaches saturation. Then, in a case where the blowing temperature of the high-
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CA 03161120 2022-05-10
concentration hydrogen-containing gas is 350 C, as shown in HG. 4, when the
gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
reaches
about 300 Nm3/t, the reduction percentage Input AC of the specific carbon
consumption
reaches a peak, and when the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas further increases, the reduction percentage Input AC
of the
specific carbon consumption starts to decrease.
In addition, in a case where the blowing temperature of the high-concentration
hydrogen-containing gas is 350 C, it is difficult to maintain the tuyere tip
temperature
Tf at 2200 C when the gas volume of the hydrogen gas in the high-concentration
hydrogen-containing gas exceeds 600 Nm3/t. In the related-art blast furnace
operation,
the flame temperature Tf is often set to about 2200 C, and in a case where it
is difficult
to maintain the flame temperature Tf at 2200 C, the operation conditions of
the related-
art blast furnace operation will be changed.
[0041]
The reason why the reduction percentage Input AC of the specific carbon
consumption starts to decrease in a case where the blowing temperature of the
high-
concentration hydrogen-containing gas is 350 C is the same as above. In a case
where
the blowing temperature of the high-concentration hydrogen-containing gas is
600 C,
the reduction percentage Input AC of the specific carbon consumption does not
start to
decrease in a range of the gas volume up to 700 Nm3/t. However, when the gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
is about
600 Nm3/t, the effect of reducing the specific carbon consumption reaches
saturation.
In a case where the blowing temperature is higher than 350 C and 600 C or
lower, the
sensible heat of the Bosch gas is larger. Therefore, since the influence of
endothermic
heat due to the hydrogen reduction reaction is reduced, the temperature inside
the
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CA 03161120 2022-05-10
furnace is considered unlikely to drop even if more hydrogen gas is blown than
in the
above case. Therefore, it is considered that even when a large amount of
hydrogen gas
is blown into the blast furnace, the temperature inside the furnace does not
easily
decrease and the reduction efficiency is unlikely to decrease. For this
reason, the
reduction percentage Input AC of the specific carbon consumption is considered
to have
reached saturation. Moreover, in a case where the gas volume of the hydrogen
gas in
the high-concentration hydrogen-containing gas is 300 to 600 Nm3/t, the
reduction
percentage Input AC of the specific carbon consumption is 10% or more.
[0042]
As shown in FIGS. 6 and 7, even in a case where the blowing temperature is
higher than 600 C and 900 C or lower, the reduction percentage Input AC of the
specific carbon consumption increases when the gas volume of the hydrogen gas
in the
high-concentration hydrogen-containing gas is increased from 0 Nm3/t in the
base
operation. Then, in a case where the gas volume of the hydrogen gas in the
high-
concentration hydrogen-containing gas is within a range of 125 Nm3/t or more,
the
reduction percentage Input AC of the specific carbon consumption is 7% or
more. In
particular, in a case where the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas is within a range of 180 Nrn3/t or more, the reduction
percentage Input AC of the specific carbon consumption is 10% or more.
Moreover, as
the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing gas
increases, the increase rate of the reduction percentage Input AC of the
specific carbon
consumption (increase amount of the reduction percentage Input AC of the
specific
carbon consumption to the unit increase amount of the gas volume) decreases.
However, the reduction percentage Input AC of the specific carbon consumption
does
not start to decrease. This behavior is clearly different from the case where
the
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CA 03161120 2022-05-10
blowing temperature of the high-concentration hydrogen-containing gas is 600 C
or
lower. FIG. 7 is a graph showing the correlation between the gas volume of the
hydrogen gas in the high-concentration hydrogen-containing gas and the
reduction
percentage Input AC of the specific carbon consumption in a case where the
blowing
temperature of the high-concentration hydrogen-containing gas (here, the pure
hydrogen
gas) is 900 C. The same tendency as in FIG. 7 was observed even in a case
where the
blowing temperature of the high-concentration hydrogen-containing gas was 650
C.
For example, as shown in FIG. 6, in a case where the blowing temperature of
the high-
concentration hydrogen-containing gas is 650 C and the gas volume of the high-
concentration hydrogen-containing gas is 125 Nin3/t or more, the reduction
percentage
Input AC the specific carbon consumption is 7.0% or more.
[0043]
As described above, since the reduction reaction caused by the hydrogen gas is
an endothermic reaction, when the gas volume of the hydrogen gas in the high-
concentration hydrogen-containing gas increases to some extent, the reduction
percentage Input AC of the specific carbon consumption starts to decrease.
However,
if the blowing temperature of the high-concentration hydrogen-containing gas
is higher
than 600 C, the sensible heat of the Bosch gas generated in the blast furnace
becomes
extremely high. Thus, the reaction heat required for the reduction reaction
can be
covered. For this reason, it is considered that even when the gas volume of
the
hydrogen gas in the high-concentration hydrogen-containing gas increases, the
reduction percentage Input AC of the specific carbon consumption does not
start to
decrease but continues to increase. Such behavior is observed in a case where
the
blowing temperature of the high-concentration hydrogen-containing gas is
higher than
600 C. Therefore, from the viewpoint of further increasing the reduction
percentage
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CA 03161120 2022-05-10
Input AC of the specific carbon consumption, the upper limit of the gas volume
of the
hydrogen gas in the high-concentration hydrogen-containing gas is not
separately set.
However, as the gas volume of the hydrogen gas in the high-concentration
hydrogen-
containing gas increases, the increase rate of the reduction percentage Input
AC of the
specific carbon consumption decreases. Therefore, it is assumed that the
effect of
reducing the specific carbon consumption reaches a peak with a certain gas
volume.
The gas volume in this case is assumed to be approximately 1000 Nm3/t.
Therefore,
the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing gas
may be 1000 Nm3/t or less.
[0044]
As shown in FIGS. 8 and 9, even in a case where the blowing temperature is
higher than 900 C and 1200 C or lower, the reduction percentage Input AC of
the
specific carbon consumption increases when the gas volume of the hydrogen gas
in the
high-concentration hydrogen-containing gas is increased from 0 Nm3/t Nm in the
base
operation. Then, in a case where the gas volume of the hydrogen gas in the
high-
concentration hydrogen-containing gas is within a range of 110 Nm3/t or more,
the
reduction percentage Input AC of the specific carbon consumption is 7% or
more. In
particular, in a case where the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas is within a range of 150 Nm3/t or more, the reduction
percentage Input AC of the specific carbon consumption is 10% or more.
Moreover,
similar to the case where the blowing temperature of the high-concentration
hydrogen-
containing gas becomes higher than 600 C and 900 C or lower, as the gas volume
of the
hydrogen gas in the high-concentration hydrogen-containing gas increases, the
increase
rate of the reduction percentage Input AC of the specific carbon consumption
decreases.
However, the reduction percentage Input AC of the specific carbon consumption
does
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CA 03161120 2022-05-10
not start to decrease. FIG. 9 is a graph showing the correlation between the
gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
and the
reduction percentage Input AC of the specific carbon consumption in a case
where the
blowing temperature of the high-concentration hydrogen-containing gas (here,
pure
hydrogen gas) is 1200 C. The same tendency as in FIG. 9 was observed even in a
case
where the blowing temperature of the high-concentration hydrogen-containing
gas was
950 C. For example, as shown in FIG. 8, in a case where the blowing
temperature of
the high-concentration hydrogen-containing gas is 950 C and the gas volume of
the
high-concentration hydrogen-containing gas is 110 Nm3/t or more, the specific
carbon
consumption reduction percentage Input AC is 7.0% or more.
[0045]
Therefore, from the viewpoint of further increasing the reduction percentage
Input AC of the specific carbon consumption, the upper limit of the gas volume
of the
hydrogen gas in the high-concentration hydrogen-containing gas is not
separately set.
However, in a case where the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas is about 1000 Nm3/t, it is assumed that the effect of
reducing
the specific carbon consumption reaches a peak. Therefore, the gas volume of
the
hydrogen gas in the high-concentration hydrogen-containing gas may be 1000
Nin3/t or
less.
[0046]
In addition, according to the blast furnace operation simulation, in a case
where
the blowing temperature of the high-concentration hydrogen-containing gas is
1200 C
and the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing
gas is 800 Nin3/t or more, the gas volume of the pulverized coal becomes 0,
and it is
possible to further reduce the specific carbon consumption by reducing a coke
ratio.
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CA 03161120 2022-05-10
Generally, in the blast furnace operation, a decrease in the coke ratio causes
an increase
in the pressure loss, resulting in unstable operation. Here, the pressure loss
is a
difference between the pressure at the tuyere tip (the outlet of the tuyere),
in other
words, the pressure inside the furnace at an outlet of the tuyere and the
pressure at the
top of the furnace, and a value excluding the pipe pressure loss from a blower
to the
tuyere tip. In the actual operation, the pressure loss is measured by a
pressure gauge
installed on a furnace wall portion. However, as shown in HG. 14, in the blast
furnace
operation under the high hydrogen concentration condition as in the present
embodiment, the gas viscosity and the gas density in the furnace decrease
significantly.
Therefore, the concern about an increase in the pressure loss when the coke
ratio is
reduced is resolved, and the pressure loss is such that there is no problem
with stable
operation in the actual operation. In addition, FIG. 14 is a graph showing the
correlation between the gas volume of the pure hydrogen gas at 1200 C and the
change
amount of the pressure loss inside the furnace when the flame temperature
reaches
2100 C, which is obtained by the blast furnace operation simulation. The
pressure loss
in normal operation is about 85 kPa as a standard. According to FIG. 14, it
can be
seen that the pressure loss is less than 85 kPa under the operation conditions
of the
present embodiment.
[0047]
As shown in FIG. 10, even in a case where the blowing temperature is higher
than 1200 C, the reduction percentage Input AC of the specific carbon
consumption
increases when the gas volume of the hydrogen gas in the high-concentration
hydrogen-
containing gas is increased from 0 Nin3/t Nm in the base operation. Then, in a
case
where the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing gas is within a range of 100 Nm3/t or more, the reduction
percentage Input
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CA 03161120 2022-05-10
AC of the specific carbon consumption is 7% or more. Moreover, similar to the
case
where the blowing temperature of the high-concentration hydrogen-containing
gas
becomes higher than 600 C and 900 C or lower, as the gas volume of the
hydrogen gas
in the high-concentration hydrogen-containing gas increases, the increase rate
of the
reduction percentage Input AC of the specific carbon consumption decreases.
However, the reduction percentage Input AC of the specific carbon consumption
does
not start to decrease. Therefore, front the viewpoint of further increasing
the reduction
percentage Input AC of the specific carbon consumption, the upper limit of the
gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
is not
separately set. However, in a case where the gas volume of the hydrogen gas in
the
high-concentration hydrogen-containing gas is about 1000 Nm3/t, it is assumed
that the
effect of reducing the specific carbon consumption reaches a peak. Therefore,
the gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
may be
1000 Nm3/t or less.
[0048]
The upper limit of the blowing temperature is not particularly limited as long
as the environment allows the blowing temperature of the high-concentration
hydrogen-
containing gas to exceed 600 C. However, as shown in FIGS. 15 and 16, the
effect of
reducing the specific carbon consumption is almost unchanged in a range where
the
blowing temperature of the high-concentration hydrogen-containing gas is in a
range of
higher than 1200 C to about 1400 C. In addition, FIGS. 15 and 16 are graphs
showing
the correlation between the blowing temperature of the pure hydrogen gas and
the gas
volume of the pure hydrogen gas required to set the reduction percentage Input
AC of
the specific carbon consumption to 10% or 20%. The flame temperature Tf was
set to
2100 C. These graphs are obtained by organizing the correlation between FIGS.
2 to
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CA 03161120 2022-05-10
by the correlation of the blowing temperature of the pure hydrogen gas and the
gas
volume of the pure hydrogen gas required to set the reduction percentage Input
AC of
the specific carbon consumption to 10% or 20%. Therefore, the blowing
temperature
of the high-concentration hydrogen-containing gas may be 1400 C or lower. That
is,
the blowing temperature of the high-concentration hydrogen-containing gas may
be, for
example, higher than 600 C and 1400 C or lower.
[0049]
Next, the high-concentration hydrogen-containing gas is blown from the tuyere
at the determined blowing temperature and gas volume. Accordingly, the
reduction
percentage Input AC of the specific carbon consumption can be set to, for
example, 7%
or more, and the CO2 emissions can be significantly reduced. In addition, the
tuyere
for blowing the high-concentration hydrogen-containing gas is, for example, a
tuyere
for blowing hot blast provided at the lower part of the furnace. The present
embodiment is described based on the premise that the high-concentration
hydrogen-
containing gas is blown from the tuyere for blowing hot blast. However, the
tuyere for
blowing the high-concentration hydrogen-containing gas is not limited to this.
Another example of the tuyere is so-called shaft tuyeres provided on a shaft
portion.
The high-concentration hydrogen-containing gas may be blown into the blast
furnace
from any of these tuyeres or may be blown into the blast furnace from both
tuyeres. In
a case where the high-concentration hydrogen-containing gas is blown into the
blast
furnace from a plurality of tuyeres, the total gas volume of the hydrogen gas
in the high-
concentration hydrogen-containing gas blown from each tuyere matches the above-
determined gas volume.
[0050]
In addition, by appropriately setting the hydrogen gas blowing temperature,
the
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CA 03161120 2022-05-10
gas volume, the flame temperature Tf, and the like under the conditions of the
present
embodiment, the operation of appropriately maintaining the top gas temperature
is
possible. For this reason, it is unnecessary to blow in the preheated gas or
preheat the
charges inside the furnace, which is performed to maintain the top gas
temperature, but
these may be separately performed.
[0051]
<4. Modification examples>
(4-1. Modification Example 1)
Hereinafter, various modification examples of the blast furnace operation
method will be described. In Modification Example 1, the flame temperature Tf
is
maintained at 2050 C or lower. Here, the flame temperature is 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 Tf'. In the actual operation, the
flame
temperature TI is calculated as a tuyere tip theoretical combustion
temperature
according to a Lamm equation described in "Ironmaking Handbook" (Chijinshokan
Co.,
Ltd.), Akitoshi SHIGEMI.
[0052]
As shown in FIGS. 2, 3, 5, 7, and 9, the reduction percentage Input AC of the
specific carbon consumption in a case where the flame temperature Tf is 2050 C
or
lower (2000 C in FIGS. 2, 3, 5, 7, and 9) is larger than the reduction
percentage Input
AC of the specific carbon consumption in a case where the flame temperature Tf
is
higher than 2050 C (2100 C and 2200 C in FIGS. 2, 3, 5, 7, and 9). Thus, in
Modification Example 1, the flame temperature Tf is maintained at 2050 C or
lower.
Accordingly, the reduction percentage Input AC of the specific carbon
consumption can
be further increased. In addition, as shown in FIGS. 7 and 9, in a case where
the
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CA 03161120 2022-05-10
blowing temperature of the high-concentration hydrogen-containing gas is
higher than
600 C and in a case where the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas is 400 Nm3/t or more, this tendency appears
remarkably.
Therefore, in a case where the blowing temperature of the high-concentration
hydrogen-
containing gas is higher than 600 C and the gas volume of the hydrogen gas in
the high-
concentration hydrogen-containing gas is 400 Nm3/t or more, the flame
temperature Tf
may be set to 2050 C or lower.
[0053]
Here, since the blowing temperature of the high-concentration hydrogen-
containing gas is lower than that of the hot blast, the flame temperature Tf
is lowered by
blowing the high-concentration hydrogen-containing gas in the blast furnace.
In order
to set the flame temperature Tf to a desired temperature. that is, to increase
the flame
temperature Tf, it is necessary to increase the oxygen enrichment ratio to
perform the
operation. Here, the hot blast blown into the blast furnace is a gas including
air. The
hot blast may include hygroscopic moisture and enriched oxygen in addition to
air.
The oxygen enrichment ratio is roughly the volume ratio of oxygen in the hot
blast to
the total volume of the hot blast, and "oxygen enrichment ratio (%) = [(blast
volume
(flow rate) [Nm3/inin] x 0.21 + amount of enriched oxygen [Nm3/min] / (blast
volume
[Nm3/min] + amount of enriched oxygen [Nin3/minD) x 100 -21". In the actual
operation, the oxygen enrichment ratio is adjusted by changing the flow rate
of enriched
oxygen in units of Nm3/t and the flow rate of air without changing the flow
rate of
oxygen, which is the total flow rate of the enriched oxygen in units of Nm3/t
and oxygen
in the hot blast. This is to keep the tapped iron ratio (daily tapped iron
amount per m3
volume inside the furnace) as constant as possible. Therefore, when the oxygen
enrichment ratio increases, the flow rate of hot blast decreases. As a result,
the amount
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of the Bosch gas decreases.
[0054]
Therefore, as the flame temperature Tf is higher, the amount of the Bosch gas
decreases. Then, when the amount of the Bosch gas decreases, the sensible heat
of the
Bosch gas decreases. Therefore, the temperature inside the furnace tends to
decrease
due to the endothermic heat generated by the hydrogen reduction reaction.
Then, in
order to prevent such a decrease in the temperature inside the furnace, it is
necessary to
perform an operation in which the reducing material ratio is increased. For
this reason,
it is considered that the reduction percentage Input AC of the specific carbon
consumption in a case where the flame temperature Tf is 2050 C or lower is
larger than
the reduction percentage Input AC of the specific carbon consumption in a case
where
the flame temperature Tf is larger than 2050 C.
[0055]
In addition, from the viewpoint of heat transfer to the molten iron and
pulverized coal combustibility, the flame temperature Tf is preferably 2000 C
or higher.
However, if the reduction percentage Input AC of the specific carbon
consumption can
be sufficiently large and the pulverized coal ratio (the pulverized coal used
per ton of
molten iron) can be sufficiently lowered, the flame temperature Tf may be
lower than
2000 C. For example, if the reduction percentage Input AC of the specific
carbon
consumption can be maintained even if the flame temperature Tf is lower than
2000 C
and a stable operation is possible, the flame temperature Tf may be set to
lower than
2000 C. In this respect, for example, as described above, in a case where the
blowing
temperature of the high-concentration hydrogen-containing gas is 1200 C and
the gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
is 800
Nm3/t or more, the gas volume of the pulverized coal is 0 (that is, the
pulverized coal
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ratio is 0). In this case, since it is not necessary to consider the
combustion of the
pulverized coal, the reduction percentage Input AC of the specific carbon
consumption
can be maintained even when the flame temperature Tf is lower than 2000 C, and
a
stable operation becomes possible. Therefore, the flame temperature Tf can be
set to
lower than 2000 C. That is, if the gas volume of the pulverized coal can be
set to 0 as
a result of raising the blowing temperature of the high-concentration hydrogen-
containing gas and increasing the gas volume, the flame temperature Tf may be
set to
lower than 2000 C.
[0056]
(4-2. Modification Example 2)
In Modification Example 2, the flame temperature Tf is maintained higher than
2050 C and lower than 2150 C. According to Modification Example 1, the
reduction
percentage Input AC of the specific carbon consumption can be increased by
setting the
flame temperature Tf to 2050 C or lower. On the other hand, when the flame
temperature Tf decreases, there is a possibility of the combustion rate of the
pulverized
coal decreasing. That is, when the flame temperature Tf decreases, the
pulverized coal
is unlikely to combust. In a case where the pulverized coal is flame-retardant
or in a
case where the operation is performed by increasing the pulverized coal ratio,
the
possibility of the combustion rate of the pulverized coal decreasing is
further increased.
When the combustion rate of the pulverized coal decreases, the temperature
inside the
furnace decreases. Thus, it may be necessary to perform an operation in which
the
reducing material ratio is increased accordingly. From this point of view, in
Modification Example 2, the flame temperature Tf is maintained higher than
2050 C
and lower than 2150 C. Accordingly, the combustion rate of the pulverized coal
can
be maintained, and a decrease in the temperature inside the furnace can be
suppressed.
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[0057]
(4-3. Modification Example 3)
In Modification Example 3, the flame temperature Tf is maintained higher than
2150 C. In the related-art blast furnace operation, the flame temperature Tf
is often set
to about 2200 C. Therefore, by setting the flame temperature Tf to higher than
2150 C, the operation can be performed without significantly changing the
operation
conditions from the related-art blast furnace operation. In addition, from the
viewpoint
of protecting the tuyere equipment, the flame temperature Tf is preferably
2250 C or
lower.
[0058]
(4-4. Modification Example 4)
As shown in FIGS. 2 to 10, there is a certain correlation between the gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
and the
reduction percentage Input AC of the specific carbon consumption. Thus, in
Modification Example 4, a gas volume-specific carbon consumption reduction
percentage correlation, which is the correlation between the gas volume of the
hydrogen
gas in the high-concentration hydrogen-containing gas and the reduction
percentage
Input AC of the specific carbon consumption, is obtained in advance.
[0059]
For example, the reduction percentage Input AC of the specific carbon
consumption for each of several gas volumes is obtained by the blast furnace
operation
simulation in which the current blast furnace operation including the blowing
temperature of the high-concentration hydrogen-containing gas is reflected.
The
specific method may be the same as that of the examples described below.
[0060]
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Next, the values obtained by the above method are plotted on a plane where the
horizontal axis is the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas in units of Nm3/t and the vertical axis is the
reduction
percentage Input AC(%) of the specific carbon consumption. Next, the
approximation
curve from these plots may be obtained by, for example, the least squares
method, and
the approximation curve, more specifically, a relational expression showing
the
approximation curve, may be used as the above-described gas volume-specific
carbon
consumption reduction percentage correlation. It is preferable to obtain the
gas
volume and the specific carbon consumption reduction percentage correlation
for each
flame temperature Tf.
[0061]
Next, the gas volume at which the reduction percentage Input AC of the
specific carbon consumption is larger than that of the current operation, that
is, the gas
volume at which the carbon consumption amount is reduced, is determined on the
basis
of the gas volume-specific carbon consumption reduction percentage correlation
obtained above. Next, the high-concentration hydrogen-containing gas is blown
from
the tuyere at the determined gas volume. Accordingly, the reduction percentage
Input
AC of the specific carbon consumption can be more reliably increased.
[0062]
Here, it is preferable to obtain the gas volume-specific carbon consumption
reduction percentage correlation in advance for each blowing temperature of
the high-
concentration hydrogen-containing gas. Accordingly, even in a case where the
blowing temperature fluctuates, the desired gas volume of the hydrogen gas in
the high-
concentration hydrogen-containing gas can be easily determined. That is, even
in a
case where the blowing temperature fluctuates, it is possible to easily
determine the gas
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volume of the hydrogen gas in the high-concentration hydrogen-containing gas
in which
the reduction percentage Input AC of the specific carbon consumption becomes
large.
[0063]
(4-5. Modification Example 5)
FIG. 12 is a graph showing, for each flame temperature Tf, the correlation
between the gas volume of the pure hydrogen gas at room temperature in units
of Nm3/t
and the change amount of the pressure loss in units of kPa with respect to the
base
operation, which is an operation in which the high-concentration hydrogen-
containing
gas is not blown. This graph is obtained from a blast furnace operation
simulation.
The details will be described in the examples. Here, the pressure loss is a
difference
between the pressure at the tuyere tip (the outlet of the tuyere), in other
words, the
pressure inside the furnace at an outlet of the tuyere and the pressure at the
top of the
furnace, and a value excluding the pipe pressure loss from a blower to the
tuyere tip.
In the actual operation, the pressure loss is measured by a pressure gauge
installed on a
furnace wall portion. The change amount of the pressure loss with respect to
the base
operation is a value obtained by subtracting the pressure loss during the base
operation
from the pressure loss during a certain operation. It is preferable that the
pressure loss
be almost the same as that of the base operation or a value lower than that of
the base
operation from the viewpoint of the restriction of the blast pressure, the
prevention of
blow-by, and the like. FIG. 12 shows the above correlation in a case where the
pure
hydrogen gas at room temperature is used. The above correlation can also be
obtained
in a case where the high-concentration hydrogen-containing gas other than the
pure
hydrogen gas is used. Additionally, even when the blowing temperature of the
high-
concentration hydrogen-containing gas is higher than room temperature, the
above
correlation can be obtained.
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[0064]
As is clear from FIG. 12, there is a certain correlation between the gas
volume
of the hydrogen gas in the high-concentration hydrogen-containing gas and the
change
amount of the pressure loss. For example, in a case where the gas volume of
the
hydrogen gas in the high-concentration hydrogen-containing gas is increased,
the flame
temperature Tf decreases as described above. In order to set the flame
temperature to a
desired temperature, it is necessary to increase the oxygen enrichment ratio
to perform
the operation. In the actual operation, the oxygen enrichment ratio is
adjusted while
the tapped iron amount is kept at a predetermined amount by changing the flow
rate of
enriched oxygen in units of Nm3/t and the flow rate of air without changing
the flow
rate of oxygen, which is the total flow rate of the enriched oxygen and oxygen
in the hot
blast in units of Nm3/t. Therefore, when the oxygen enrichment ratio
increases, the
flow rate of hot blast decreases. As a result, the amount of the Bosch gas
decreases.
In other words, in a case where the flame temperature Tf is low, the amount of
the
Bosch gas increases. As a result, there is a possibility of the pressure loss
being larger
than that of the base operation. However, when the gas volume of the hydrogen
gas in
the high-concentration hydrogen-containing gas is further increased, the gas
viscosity
and gas density of the gas in the furnace are lowered, and the pressure loss
is reduced.
Then, the decrease in pressure loss caused by the decrease in gas viscosity
and gas
density offsets the increase in the pressure loss caused by the increase in
the amount of
the Bosch gas, and as a result, the pressure loss decreases.
[0065]
In Modification Example 5, first, the gas volume-specific carbon consumption
reduction percentage correlation is obtained in advance similar to
Modification Example
4. Moreover, a gas volume-pressure drop change correlation, which is the
correlation
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between the gas volume and the change amount of the pressure loss with respect
to the
base operation, is obtained.
[0066]
For example, the change amount of the pressure loss for each of several gas
volumes is obtained by the blast furnace operation simulation in which the
current blast
furnace operation including the blowing temperature of the high-concentration
hydrogen-containing gas is reflected. The specific method may be the sante as
that of
the examples described below.
[0067]
Next, the values obtained by the above method are plotted on a plane where the
horizontal axis is the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas in units of Nm3/t and the vertical axis is A pressure
loss that is
the change amount of the pressure loss in units of kPa. Next, the
approximation curve
from these plots may be obtained by, for example, the least squares method,
and the
approximation curve (more specifically, a relational expression showing the
approximation curve) may be used as the above-described gas volume-pressure
drop
change correlation. The gas volume-pressure drop change correlation is
preferably
obtained for each flame temperature Tf.
[0068]
Next, the reduction percentage Input AC of the specific carbon consumption is
larger than that of the current operation, that is, the carbon consumption
amount is
reduced and the gas volume in which the change amount of the pressure loss is
a value
within a predetermined range is determined on the basis of the gas volume-
specific
carbon consumption reduction percentage correlation and the gas volume-
pressure drop
change correlation. Here, the predetermined range is, for example, about ¨50
to +5
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kPa, but is not limited to this. Next, the high-concentration hydrogen-
containing gas is
blown from the tuyere at the determined gas volume. Accordingly, the reduction
percentage Input AC of the specific carbon consumption can be more reliably
increased
while the change amount of the pressure loss is set to a value within a
predetermined
range.
[0069]
(4-6. Modification Example 6)
FIG. 13 is a graph showing the correlation between the gas volume of the pure
hydrogen gas in units of Nin3/t at room temperature and the change amount of
the top
gas temperature with respect to the base operation in units of C for each
flame
temperature If. This graph is obtained from a blast furnace operation
simulation.
The details will be described in the examples. Here, the top gas temperature
is the
temperature of the furnace top gas (mainly CO2, N2, unreacted CO, or the like)
discharged from the top of the blast furnace, and in the actual operation, is
measured by
a thermometer installed on a riser tube or the like. The change amount of the
top gas
temperature with respect to the base operation is a value obtained by
subtracting the top
gas temperature during the base operation from the top gas temperature during
a certain
operation. The top gas temperature is preferably almost the same as that of
the base
operation from the viewpoint of restrictions on furnace top equipment and
efficient
operation, and as an example, is preferably within a range of about 20 C
from the top
gas temperature of the base operation. FIG. 13 shows the above correlation in
a case
where the pure hydrogen gas at room temperature is used The above correlation
can
also be obtained in a case where the high-concentration hydrogen-containing
gas other
than the pure hydrogen gas is used. Additionally, even when the blowing
temperature
of the high-concentration hydrogen-containing gas is higher than room
temperature, the
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above correlation can be obtained.
[0070]
As is clear from FIG. 13, there is a certain correlation between the gas
volume
of the hydrogen gas in the high-concentration hydrogen-containing gas and the
change
amount of the top gas temperature. For example, in a case where the gas volume
of
the hydrogen gas in the high-concentration hydrogen-containing gas is
increased, the
flame temperature Tf decreases as described above. In order to set the flame
temperature Tf to a desired temperature, it is necessary to increase the
oxygen
enrichment ratio to perform the operation. In the actual operation, the oxygen
enrichment ratio is adjusted by changing the flow rate of air in units of
Nm3/t without
changing the flow rate of oxygen in units of Nm3/t. Therefore, when the oxygen
enrichment ratio increases, the flow rate of hot blast decreases. As a result,
the amount
of the Bosch gas decreases. In other words, when the flame temperature Tf
rises, the
amount of the Bosch gas decreases. For this reason, a heat flow ratio
expressed by
(heat capacity of charges inside furnace falling per unit time)/(heat capacity
of Bosch
gas rising per unit time) increases. As a result, the temperature of the gas
inside the
furnace that rises inside the furnace tends to decrease, and as a result, the
top gas
temperature tends to decrease. As a result, there is a possibility of the top
gas
temperature being lower than that of the base operation. However, when the gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
is
further increased, the temperature inside the furnace drops due to the
endothermic
reaction as described above with approximately 300 Nm3/t as a boundary, and
the
reduction efficiency begins to decrease. In order to prevent such a decrease
in
reduction efficiency, the operation is performed by increasing the reducing
material
ratio. However, when the reducing material ratio is increased, the amount of
heat input
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into the furnace increases and the top gas temperature tends to rise.
Therefore, the top
gas temperature starts to increase.
[0071]
In Modification Example 6, first, the gas volume-specific carbon consumption
reduction percentage correlation is obtained in advance similar to
Modification Example
4. Moreover, a gas volume-top gas temperature change amount correlation,
which is
the correlation between the gas volume and the change amount of the top gas
temperature with respect to the base operation, is obtained.
[0072]
For example, the change amount of the top gas temperature for each of several
gas volumes is obtained from the blast furnace operation simulation in which
the current
blast furnace operation including the blowing temperature of the high-
concentration
hydrogen-containing gas is reflected. The specific method may be the same as
that of
the examples described below.
[0073]
Next, the values obtained by the above method are plotted on a plane where the
horizontal axis is the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas in units of Nm3/t and the vertical axis in the unit
kPa is A top
gas temperature that is the change amount of the top gas temperature in units
of C.
Next, the approximation curve from these plots may be obtained by, for
example, the
least squares method, and the approximation curve, more specifically, a
relational
expression showing the approximation curve, may be used as the above-described
gas
volume-top gas temperature change amount correlation. The gas volume-top gas
temperature change amount correlation is preferably obtained for each flame
temperature Tf.
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[0074]
Next, the gas volume in which the reduction percentage Input AC of the
specific carbon consumption is larger than that of the current operation, that
is, the
carbon consumption amount is reduced and in which the change amount of the top
gas
temperature is a value within a predetermined range is determined on the basis
of the
gas volume-specific carbon consumption reduction percentage correlation and
the gas
volume-top gas temperature change amount correlation. Here, the predetermined
range is, for example, about ¨20 to + 20 C, but is not limited thereto. Next,
the high-
concentration hydrogen-containing gas is blown from the tuyere at the
determined gas
volume. Accordingly, the reduction percentage Input AC of the specific carbon
consumption can be more reliably increased while the change amount of the top
gas
temperature is set to a value within a predetermined range.
[0075]
Here, in the above Modification Examples 4 to 6, the parameter paired with the
gas volume of the hydrogen gas in the high-concentration hydrogen-containing
gas is
not necessarily limited to the reduction percentage Input AC of the specific
carbon
consumption. That is, the parameter paired with the gas volume of the hydrogen
gas in
the high-concentration hydrogen-containing gas may be any parameter related to
the
carbon consumption amount, that is, any carbon consumption parameter. This is
because if the carbon consumption amount is reduced, the CO2 emissions can be
reduced. Examples of such a carbon consumption parameter include the specific
carbon consumption, the reducing material ratio, the reduction percentage of
the
reducing material ratio, and the like in addition to the reduction percentage
Input AC of
the specific carbon consumption. The reduction percentage of the reducing
material
ratio is the reduction percentage of the reducing material ratio with respect
to the base
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operation, and the calculation method is the same as the calculation method of
the
reduction percentage Input AC of the specific carbon consumption.
[0076]
Moreover, Modification Example 5 and Modification Example 6 may be
combined with each other. Accordingly, the reduction percentage Input AC of
the
specific carbon consumption can be more reliably increased while the change
amount of
the pressure loss and the change amount of the top gas temperature are set to
values
within a predetermined ranges.
[Examples]
[0077]
Next, examples of the present embodiment will be described. In the present
embodiment, it was confirmed by performing the blast furnace operation
simulation that
the reduction percentage Input AC of the specific carbon consumption increases
due to
the blast furnace operation method according to the present embodiment, that
is, the
CO2 emissions are reduced.
[0078]
<1. Example I: Verification in a case where blowing temperature of high-
concentration hydrogen-containing gas is room temperature to 600 C>
As described above, the correlation between the gas volume of the hydrogen
gas in the high-concentration hydrogen-containing gas and the reduction
percentage
Input AC of the specific carbon consumption shows a different behavior with
the
blowing temperature of 600 C as a boundary. Thus, in Example I, verification
was
performed in a case where the blowing temperature of the high-concentration
hydrogen-
containing gas was 600 C or lower.
[0079]
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<1-1. Model and calculation conditions used for simulation>
As the blast furnace operation simulation, a so-called "Blast Furnace
Mathematical Model" Kouji TAKATANI, Takanobu 1NADA, Yutaka UJISAWA,
"Three-dimensional Dynamic Simulator for Blast Furnace", ISIJ International,
Vol. 39
(1999), No. 1, pp. 15 to 22 was 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.
[0080]
In the blast furnace mathematical model, the gas volume of the high-
concentration hydrogen-containing gas is set as the amount of the high-
concentration
hydrogen-containing gas blown from the tuyere. Of these, the gas volume of the
hydrogen gas in the high-concentration hydrogen-containing gas is set as the
amount
obtained by multiplying the gas volume of the high-concentration hydrogen-
containing
gas by the ratio of the hydrogen gas in units of mol%. The blowing temperature
of the
high-concentration hydrogen-containing gas is set as the temperature of the
high-
concentration hydrogen-containing gas when the high-concentration hydrogen-
containing gas is blown from the tuyere. The flame temperature Tf is
calculated as a
result of considering the combustion heat of various gases, the sensible heat
of blast, the
temperature of the coke flowing into the tuyere tip (the outlet of the
tuyere), various
reaction heats, and the like. The pressure loss is calculated using the Ergun
equation
as the pressure loss of a packed bed inside the furnace. The top gas
temperature is
calculated as the gas temperature in the outermost layer (uppermost layer) of
the
charges inside the furnace.
[0081]
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The calculation conditions are shown in Table 1. The coke ratio in Table 1 is
the amount of coke used per ton of molten iron. Additionally, Table 2 shows
the
specifications of the base operation in which high-concentration hydrogen-
containing
gas is not blown in. As shown in Tables 1 and 2, in the present example, the
flame
temperature Tf was set to any of 2000 C, 2100 C, or 2200 C. Additionally, the
gas
volume of the hydrogen gas in the high-concentration hydrogen-containing gas
was set
to 0 to 600 Nm3/t. Additionally, the blast volume, the oxygen enrichment
ratio, and
the gas volume of PC (pulverized coal) were adjusted such that the tapped iron
ratio and
the molten iron temperature were constant in all operations.
[0082]
[Table 1]
Calculation conditions
Tapped iron ratio t/d/m3 About 2.7 (Constant)
Molten iron temperature C 1535 to 1540
Blast volume Nm3/min Adjusted
Oxygen enrichment ratio Adjusted
Pre-tuyere temperature C 2000, 2100, 2200
Gas volume of hydrogen gas into
high-concentration hydrogen- Nm3/t 0 to 600
containing gas
Blowing temperature of high-
concentration hydrogen-containing pc 25 to 600
gas
Coke ratio kg/t 300 (Constant)
Gas volume of pulverized coal tons/h Adjusted
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[0083]
[Table 2]
Base operation specifications at pre-tuyere temperatures of 2000 C, 2100 C,
and 2200 C
2000 C 2100 C 2200 C
Tapped ion ratio t/d/m3 2.74 2.74 2.74
Blast volume Nm3/min 9440 7800 6300
Oxygen enrichment ratio (7c 1.2 4.8 9.2
Gas volume of hydrogen gas into high-
lf/t 0 0 0
concentration hydrogen-containing gas
Coke ratio kg/t 306.6 306.6 306.6
Pulverized coal ratio kg/t 201.4 200.1 200.2
Molten iron temperature C 1537 1536 1536
[0084]
In addition, the iron-bearing materials were all sintered ores. Additionally,
the composition of the sintered ores was T-Fe: 58.5%, FeO: 7.5%, C/S: 1.9, and
A1203:
1.7%. Additionally, regarding coke, a case where C: 87.2% and ash: 12.6% was
used
was assumed. In addition, all of the above "%" represent "mass%".
[0085]
<1-2. Example 1-1: Case where blowing temperature of high-concentration
hydrogen-containing gas is room temperature to 600 C and high-concentration
hydrogen-containing gas is pure hydrogen gas>
In Example 1-1, the correlation between the gas volume of the pure hydrogen
gas and the reduction percentage Input AC of the specific carbon consumption
was
calculated using the high-concentration hydrogen-containing gas as the pure
hydrogen
gas, under the condition that the blowing temperature of the high-
concentration
hydrogen-containing gas was 600 C or lower. The results are shown in FIGS. 2
to 5.
[0086]
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As shown in FIGS. 2 to 5, it was found that, in a range where the blowing
temperature is at room temperature or higher and 600 C or lower, the reduction
percentage Input AC of the specific carbon consumption does not simply
increase with
an increase in the gas volume but reaches saturation and starts to decrease
when the gas
volume of air increases to some extent. Then, it was found that the gas volume
when
the reduction percentage Input AC of the specific carbon consumption reaches
saturation and starts to decrease is slightly different depending on the
blowing
temperature. That is, it was found that an appropriate range of the gas volume
is
present for each blowing temperature. The appropriate range was 200 to 500
Nm3/t in
a case where the blowing temperature was room temperature to 300 C and was 145
Nm3/t or more when the blowing temperature was higher than 300 C and 600 C or
lower. Additionally, as shown in FIGS. 4 and 5, it was found that the
reduction
percentage Input AC of the specific carbon consumption does not simply
increase with
an increase in the gas volume but reaches saturation at a gas volume of about
600 Nm3/t
when the blowing temperature is 600 C and starts to decrease with an increase
in the
gas volume at a gas volume peak of about 300 Nm3/t when the blowing
temperature is
350 C. Also, in a case where the blowing temperature is higher than 300 C and
600 C
or lower and the gas volume is within an appropriate range of 145 Nm3/t or
more, it is
possible to set the reduction percentage Input AC of the specific carbon
consumption to
7% or more. Moreover, as shown in FIGS. 2 to 5, it was also found that the
reduction
percentage Input AC of the specific carbon consumption with respect to the
same gas
volume varies depending on the flame temperature Tf and is the largest when
the flame
temperature Tf is 2000 C. The reason why such a phenomenon is obtained is as
described above.
[0087]
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Therefore, by blowing the high-concentration hydrogen-containing gas in the
blast furnace according to the blast furnace operation method according to the
present
embodiment, the reduction percentage Input AC of the specific carbon
consumption can
be increased, and the CO2 emissions can be significantly reduced.
[0088]
<1-3. Example 1-2>
In Example 1-2, it was confirmed that even if the high-concentration hydrogen-
containing gas contains a gas component other than the hydrogen gas, the same
operation as in the case of the pure hydrogen gas is possible. Specifically,
80 mol%
H2-20 mol% N2 gas composed of 80 mol% hydrogen gas and 20 mol% nitrogen gas
was
assumed as the high-concentration hydrogen-containing gas. Then, the blast
furnace
operation simulation was performed in the same manner as in Example 1 with the
blowing temperature set to 25 C and the flame temperature Tf set to 2100 C.
The
results are shown in FIG. 11. FIG. 11 shows a comparison between the
calculation
result of the pure hydrogen gas (100 mol% H2 gas) and the calculation result
of 80
mol% H2-20 mol% N2 gas. In addition, the horizontal axis in FIG. 11 represents
a
value obtained by converting the flow rate of a mixed gas in the pure hydrogen
gas, that
is, a value obtained by multiplying the flow rate of 80 mol% H2-20 mol% N2 gas
by 80
mol%. As is clear from FIG. 11, it was found that, for 80 mol% H2-20 mol% N2
gas,
the appropriate range of the gas volume converted into the pure hydrogen gas
is the
same as that of the pure hydrogen gas and only the effect cost decreases
slightly.
Therefore, it was found that even when the high-concentration hydrogen-
containing gas
contains a gas component other than the hydrogen gas, the same operation as in
the case
of the pure hydrogen gas is possible. Additionally, it was also found that the
reduction
percentage Input AC of the specific carbon consumption can be increased,
although the
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effect is slightly reduced.
[0089]
<1-4. Example 1-3>
In Example 1-3, the pure hydrogen gas at room temperature was used as the
high-concentration hydrogen-containing gas, and the change amount of the
pressure loss
with respect to each of several gas volumes (the change amount of the pressure
loss
with respect to the base operation) was obtained. FIG. 12 shows the results.
As is
clear from FIG. 12, it was found that there is a certain correlation between
the gas
volume of the pure hydrogen gas and the change amount of the pressure loss.
For
example, it was found that there is a possibility of the pressure loss being
large with
respect to the base operation in a case where the flame temperature Tf is low.
However, the pressure loss decreases when the gas volume of the pure hydrogen
gas
increases. More specifically, in a case where the flame temperature Tf is 2000
C and
the gas volume is 100 to 150 Nm3/t, the pressure loss increases by about 10 to
20 kPa as
compared to the base operation. This is a value outside the predetermined
range
described above. However, when the gas volume increases to 200 Nm3/t or more,
the
pressure loss is almost the same as or less than the value of the base
operation. The
reason why such a phenomenon occurs is as described above. Therefore, it was
found
that it is possible to suppress the increase in the pressure loss and increase
the unit
reduction percentage Input AC of the specific carbon consumption while
performing a
stable operation, by obtaining the gas volume-pressure drop change
correlation, which
is the correlation between the gas volume of the hydrogen gas in the high-
concentration
hydrogen-containing gas and the change amount of the pressure loss with
respect to the
base operation when the blowing temperature is a predetermined value, in
advance for
each flame temperature Tf and by determining the gas volume of the hydrogen
gas in
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the high-concentration hydrogen-containing gas at which the carbon consumption
amount is reduced compared to that of the current operation, and the change
amount of
the pressure loss is a value within a predetermined range on the basis of the
gas volume-
carbon consumption parameter correlation and the gas volume-pressure drop
change
correlation.
Then, it was found that it is possible to suppress the increase in the
pressure
loss and increase the reduction percentage Input AC of the specific carbon
consumption
while performing a stable operation as shown in FIG. 12, under the conditions
that the
pure hydrogen gas at room temperature is used as the high-concentration
hydrogen-
containing gas and the gas volume is 200 Nm3/t or more and 500 Nm3/t or less.
It was
found that when the gas volume increases to 200 Nm3/t in the case of the pure
hydrogen
gas at room temperature or higher and 300 C or lower, the pressure loss is
almost the
same as or equal to or less than the value of the base operation. Similarly,
it was found
that it is possible to suppress the increase in the pressure loss and increase
the reduction
percentage Input AC of the specific carbon consumption while performing a
stable
operation in a case where the gas volume of the pure hydrogen at higher than
300 C and
600 C or lower is 145 Nm3/t or more, even in a case where the gas volume of
the pure
hydrogen at higher than 600 C and 900 C or lower is 125 Nm3/t or more, even in
a case
where the gas volume of the pure hydrogen at higher than 900 C and 1200 C or
lower
is 110 Nm3/t or more, and even in a case where the gas volume of the pure
hydrogen at
higher than 1200 C is 100 Nm3/t or more.
[0090]
Therefore, it was found that it is possible to increase the reduction
percentage
Input AC of the specific carbon consumption while setting the change amount of
the
pressure loss to a value within a predetermined range by blowing the high-
concentration
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hydrogen-containing gas in the blast furnace according to the blast furnace
operation
method according to the present embodiment.
[0091]
<1-5. Example 1-4>
In Example 1-4, the pure hydrogen gas at room temperature was used as the
high-concentration hydrogen-containing gas, and the change amount of the top
gas
temperature with respect to each of several gas volumes (the change amount of
the top
gas temperature with respect to the base operation) was obtained. FIG. 13
shows the
results. As is clear from FIG. 13, it was found that there is a certain
correlation
between the gas volume of the pure hydrogen gas and the change amount of the
top gas
temperature. For example, when the flame temperature Tf increases, the top gas
temperature decreases as compared to the base operation. Specifically, in a
case where
the flame temperature Tf is 2100 C and the gas volume is 250 to 300 Nm3/t, the
change
amount of the top gas temperature is a value outside the above-described
predetermined
range. However, if the gas volume decreases to 200 Nm3/t, the change amount of
the
top gas temperature becomes a value within a predetermined range. The reason
why
such a phenomenon occurs is as described above. Therefore, in a case where the
efficiency of operation or the like is emphasized, the gas volume may be
adjusted in
consideration of the correlation between the gas volume of the pure hydrogen
gas and
the change amount of the top gas temperature. Therefore, it was found that it
is
possible to suppress the decrease in the efficiency of the operation by
obtaining the gas
volume-top gas temperature change amount correlation, which is the correlation
between the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing gas and the change amount of the top gas temperature with respect
to the
base operation when the blowing temperature is a predetermined value, in
advance for
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each flame temperature Tf and by determining the gas volume of the hydrogen
gas in
the high-concentration hydrogen-containing gas at which the carbon consumption
amount is reduced compared to that of the current operation, and the change
amount of
the top gas temperature is a value within a predetermined range on the basis
of the gas
volume-carbon consumption parameter correlation and the gas volume-top gas
temperature change amount correlation.
[0092]
<2. Example 2: Verification in case where blowing temperature of high-
concentration hydrogen-containing gas is higher than 600 C>
In Example 2, a case where the blowing temperature of the high-concentration
hydrogen-containing gas is higher than 600 C was verified.
[0093]
<2-1. Model and calculation conditions used for simulation>
In the blast furnace operation simulation, the same "blast furnace
mathematical
model" as in Example 1 was used. Calculation conditions are shown in Table 3.
As
shown in Table 3, the calculation conditions were almost the same as those in
Example
I, but the coke ratio was different from that in Example 1. That is, in
Example 2, the
coke ratio was constant at 300 kg/tin a case where the pulverized coal gas
volume was
larger than 0 tons/h, and the coke ratio fluctuated in a case where the
pulverized coal
gas volume was 0 tons/h (that is, in a case where the pulverized coal ratio
was 0). That
is, in a case where the gas volume of the pulverized coal was 0 tons/h, the
furnace
temperature was adjusted according to the coke ratio.
[0094]
As described above, in a case where the blowing temperature of the high-
concentration hydrogen-containing gas is increased and the gas volume is
increased, the
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gas volume of the pulverized coal may be 0 tons/h. In this case, by reducing
the coke
ratio, it is possible to further reduce the specific carbon consumption.
Additionally, the
gas volume of the hydrogen gas in the high-concentration hydrogen-containing
gas was
set to 0 to 1000 Nm3/t. Additionally, the blowing temperature of the high-
concentration hydrogen-containing gas was set to higher than 600 C and 1400 C
or
less. in addition, the specifications of the base operation in which the high-
concentration hydrogen-containing gas was not blown were the same as in
Example 1.
Other conditions were the same as those of Example 1. For example, the blast
volume,
the oxygen enrichment ratio, and the gas volume of PC (pulverized coal) were
adjusted
such that the tapped iron ratio and the molten iron temperature were constant
in all
operations. The iron-bearing materials were sintered ore used in Example 1.
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[0095]
[Table 3]
Calculation conditions
Tapped iron ratio t/d/r& About 2.7 (constant)
Molten iron temperature C 1535 to 1540
Blast volume NmVrnin Adjusted
Oxygen enrichment ratio Adjusted
Pre-tuyere temperature C 2000, 2100, 2200
Gas volume of hydrogen gas into high-
Nm3/t 0 to 1000
concentration hydrogen-containing gas
Blowing temperature of high-concentration
C Higher than 600 and 1400 or lower
hydrogen-containing gas
300 (constant in case where gas volume of
Coke ratio kg/t
pulverized coal is more than 0 tons/h)
Gas volume of pulverized coal tons/h Adjusted
[0096]
<2-2. Example 2-1: Case where blowing temperature of high-concentration
hydrogen-containing gas is higher than 600 C and high-concentration hydrogen-
containing gas is pure hydrogen gas>
In Example 2-1, the correlation between the gas volume of the pure hydrogen
gas and the reduction percentage Input AC of the specific carbon consumption
was
calculated using the high-concentration hydrogen-containing gas as the pure
hydrogen
gas. The results are shown in FIGS. 6 to 10.
[0097]
As shown in FIGS. 6 to 10, it was found that the reduction percentage Input
AC of the specific carbon consumption increases when the gas volume of the
hydrogen
gas in the high-concentration hydrogen-containing gas is increased from 0
Nm3/t in the
base operation. Moreover, as the gas volume of the hydrogen gas in the high-
concentration hydrogen-containing gas increases, the increase rate of the
reduction
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percentage Input AC of the specific carbon consumption (increase amount of the
reduction percentage Input AC of the specific carbon consumption to the unit
increase
amount of the gas volume) decreases. However, the reduction percentage Input
AC of
the specific carbon consumption did not start to decrease. This behavior was
clearly
different from the case where the blowing temperature of the high-
concentration
hydrogen-containing gas was 600 C or lower.
[0098]
In addition, a range where the reduction percentage Input AC of the specific
carbon consumption was 7% or more was different depending on the blowing
temperature of the high-concentration hydrogen-containing gas. Specifically,
in a case
where the blowing temperature was higher than 600 C and 900 C or lower and in
a case
where the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing gas was within a range of 125 Nm3/t or more, the reduction
percentage Input
AC of the specific carbon consumption was 7% or more. Additionally, in a case
where
the blowing temperature was higher than 900 C and 1200 C or lower and in a
case
where the gas volume of the hydrogen gas in the high-concentration hydrogen-
containing gas was within a range of 110 Nm3/t or more, the reduction
percentage Input
AC of the specific carbon consumption was 7% or more. In a case where the
blowing
temperature was higher than 1200 C and in a case where the gas volume of the
hydrogen gas in the high-concentration hydrogen-containing gas was within a
range of
100 Nm3/t or more, the reduction percentage Input AC of the specific carbon
consumption was 7% or more.
[0099]
<2-3. Other tests>
The same test as in Examples 1-3 and 1-4 was performed with the blowing
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temperature of the pure hydrogen gas set to 900 C. As a result, even in a case
where
the blowing temperature of the pure hydrogen gas was 900 C, it was confirmed
that
there is a certain correlation between the gas volume of the pure hydrogen gas
and the
change amount of the pressure loss or the change amount of the top gas
temperature.
[0100]
Therefore, it is possible to increase the reduction percentage Input AC of the
specific carbon consumption while setting the change amount of the top gas
temperature
to a value within a predetermined range by blowing the high-concentration
hydrogen-
containing gas in the blast furnace according to the blast furnace operation
method
according to the present embodiment.
[0101]
Although the preferred embodiment of the present invention has been
described above in detail with reference to the accompanying drawings, the
present
invention is not limited to such an example. It is apparent that those having
ordinary
knowledge in the technical field to which the present invention belongs can
conceive
various changes or alterations within the scope of the technical ideas
described in the
claims, and it is naturally understood that these also belong to the technical
scope of the
present invention.
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