AU2020393659B2 - Blast furnace operation method - Google Patents

Abstract

According to one aspect of the present invention, provided is a blast furnace operation method characterized in that a high-concentration hydrogen-containing gas which contains at least 80 mol% of hydrogen gas, is blown from a tuyere under certain conditions such as: a condition in which the blowing temperature of the high-concentration hydrogen-containing gas is room temperature to 300 °C, and the blown amount of hydrogen gas in the high-concentration hydrogen-containing gas is 200 Nm

Description

[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 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 (CO 2 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 C02 gas is

generated. Accordingly, the steel industry is one of the main industries producing CO 2

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 H 2 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 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 (H2 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 2] Japanese Patent No. 5987773

[Patent Document 3] Japanese Patent No. 5050706

[Patent Document 4] Japanese Patent No. 5770124

[Patent Document 5] Japanese Patent No. 5315732

[Patent Document 6] Japanese Patent No. 5851828

[Disclosure of the Invention]

[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 C02

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 C02 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 Nm 3/t or more and 500 Nm 3/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 hydrogen gas in the high

concentration hydrogen containing gas is 125 Nm 3/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 Nm 3/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

Nm 3/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 Nm 3 /t or

more and 300 Nm 3/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 Nm 3 /t or more and

600 Nm 3/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.

[00151

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 Nm 3/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 Nm 3/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 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 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 C02 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 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 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 I 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 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 CO 2 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 mo%).

[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 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 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 some extent, the

reduction percentage Input AC of the specific carbon consumption becomes, for

example, 7% or more. Therefore, the C02 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 C02 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 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, C02 gas, H 2 0 gas,

N 2 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 C02 gas decreases

significantly in a case where the concentration of the other gases is 20 mol% or more.

For example, since hydrocarbon gases, C02 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 C02 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 Nm/t. The

effect of reducing the C02 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 Nm 3 t,

and does not lead to a drastic reduction of the CO 2 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 C02 emissions is maximized when the gas volume is about 300 Nin 3/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 I 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 1 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 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 C02 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", ISI 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 Nm 3 /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 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

). 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.

[00331

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 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 Nm 3/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.

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 Nm 3/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 Nm 3/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 Nm 3/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 Nm 3/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 Nm 3/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]

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 3000 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 Nm 3 /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 Nm 3/t, it is possible to set the reduction percentage Input AC of the specificcarbon

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 Nm 3/t, it is considered that such an endothermic reaction

occurs frequently in the furnace and the temperature inside the furnace drops. Also, 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 Nm 3/t, and it is more preferable

to determine the gas volume within a range of 200 to 300 Nm 3/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 Nm 3 /t Nm in the base operation. Then, when the

gas volume of the hydrogen gas in the high-concentration hydrogen-containing gas is

145 Nm 3/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 concentration hydrogen-containing gas is 350°C, as shown in FIG. 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 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 Nm 3/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 Nm 3/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 Nm 3/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 Nm 3 /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 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 Nm3 /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

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 Nm 3/t. Therefore,

the gas volume of the hydrogen gas in the high-concentration hydrogen-containing gas

may be 1000 Nm 3/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 Nm 3/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 Nm 3/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 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 Nm 3/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 Nm 3/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.

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 FIG. 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. Thepressureloss

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 Nm 3/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

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, 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 Nm 3 /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 Nm 3/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 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 C02 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 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 Tf 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 0C 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 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 Nm 3/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 Nm 3/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/min] x 0.21 + amount of enriched oxygen [N1 3/min] / (blast volume

[Nm 3/min] + amount of enriched oxygen [Nm 3/min])} 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 Nm 3/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 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

Nm 3/t or more, the gas volume of the pulverized coal is 0 (that is, the pulverized coal 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.

[00571

(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]

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 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 Nm 3/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.

[00641

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 Nm 3/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 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 same 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 Nm 3 /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 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 Nm 3/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 Tf. 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 C02, 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 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 Nn 3/t without

changing the flow rate of oxygen in units of Nm 3/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 endothermiic

reaction as described above with approximately 300 Nm 3/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 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 Nm 3 /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.

[00741

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 C02 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 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

C02 emissions are reduced.

[0078]

<1. Example 1: 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 1, verification was

performed in a case where the blowing temperature of the high-concentration hydrogen

containing gas was 600°C or lower.

[0079]

<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 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.

[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]

The calculation conditions are shown in Table 1. The coke ratio in Table I 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 I 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 Nm 3/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 Nm 3/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 °C 25 to 600 gas Coke ratio kg/t 300 (Constant)

Gas volume of pulverized coal tons/h Adjusted

[00831

[Table 2] Base operation specifications at pre-tuyere temperatures of 2000°C, 2100°C, and 2200°C

2000 0 C 21000 C 22000 C t/d/in Tapped ion ratio 2.74 2.74 2.74

Blast volume NM 3 /min 9440 7800 6300

Oxygen enrichment ratio % 1.2 4.8 9.2

Gas volume of hydrogen gas into high- Nm3/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 0 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]

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 Nm 3/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 Nm 3/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 Nn1 3/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]

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 C02 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 I 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% H 2 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 80mol% H2-20 mol% N2 gas by 80

mol%. As is clear from FIG. 11, it was found that, for 80 mol%H 2 -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 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 Nm 3/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 Nm 3/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 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 Nm 3/t or more and 500 Nm 3/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 Nm 3/t or more, even in a case where the gas volume of the pure

hydrogen at higher than 600°C and 900 0C or lower is 125 Nm 3 /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 Nn1 3/t or more, and even in a case where the gas volume of the pure hydrogen at

higher than 1200°C is 100 Nm 3/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 hydrogen-containing gas in the blast furnace according to the blast furnace operation method according to the present embodiment.

[00911

<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 Nm/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 Nm 3/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 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

1, but the coke ratio was different from that in Example 1. That is, in Example 2, the

coke ratio was constant at 300 kg/t in 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 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 Nm 3/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.

[00951

[Table 3] Calculation conditions

Tapped iron ratio t/d/rn 3 About 2.7 (constant) 0 Molten iron temperature C 1535 to 1540

Blast volume Nm3/min Adjusted

Oxygen enrichment ratio % Adjusted 0 Pre-tuyere temperature C 2000,2100,2200 Gas volume of hydrogen gas into high- Nm3/t 0to1000 concentration hydrogen-containing gas Blowing temperature of high-concentration 0 C Higher than 600 and 1400 or lower hydrogen-containing gas

Coke ratio kg/t 300 (constant in case where gas volume of 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 Nm 3/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 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 Nni 3/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 Nm-/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 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.

Claims (13)

[Document Type] CLAIMS

1. 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 Nm 3/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 Nm 3/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 hydrogen gas in the high-concentration hydrogen-containing gas is 125 Nm 3/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 Nm 3/t or more.

2. The blast furnace operation method according to claim 1,

wherein the blowing temperature is higher than room temperature and 300°C or lower and the gas volume of the hydrogen gas in the high-concentration hydrogen containing gas is 200 Nm 3/t or more and 300 Nm 3/t or less.

3. The blast furnace operation method according to claim 1,

wherein 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 Nm 3/t or more

and 600 Nm 3/t or less.

4. The blast furnace operation method according to any one of claims 1 to 3,

wherein a flame temperature is 2050°C or lower.

5. The blast furnace operation method according to any one of claims I to 3,

wherein a flame temperature is higher than 2050°C and 21500 C or lower.

6. The blast furnace operation method according to any one of claims 1 to 3,

wherein a flame temperature is higher than 2150°C and 2250°C or lower.

7. The blast furnace operation method according to claim 1,

wherein the blowing temperature of the high-concentration hydrogen

containing gas is higher than 600°C and 1400°C or lower.

8. The blast furnace operation method according to claim 1 or 7,

wherein, 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 is 1000 Nm 3/t or less.

9. The blast furnace operation method according to any one of claims 1, 7,

and 8,

wherein, 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 Nm 3/t or more, a flame

temperature is set to 2050°C or lower.

10. A blast furnace operation method comprising:

obtaining a gas volume-carbon consuniption 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

determined gas volume.

11. The blast furnace operation method according to claim 10,

wherein the gas volume-carbon consumption parameter correlation is obtained for each blowing temperature.

12. The blast furnace operation method according to claim 10 or 11,

wherein 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 is a predetermined value, is 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 is determined on the basis of the gas volume-carbon consumption

parameter correlation and the gas volume-pressure drop change correlation.

13. The blast furnace operation method according to any one of claims 10 to

12,

wherein 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 is a predetermined value, is 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 top gas temperature is a value within

a predetermined range is determined on the basis of the gas volume-carbon consumption parameter correlation and the gas volume-top gas temperature change amount correlation.