JP7348466B2 - Blast furnace operating method and pig iron manufacturing method - Google Patents

Description

The present invention relates to a method of operating a blast furnace and a method of producing pig iron.

Generally, in the operation of a blast furnace, iron sources such as lump ore, sintered ore, pellets, etc., and coke are alternately charged from the top of the blast furnace. Inside the blast furnace, ore layers formed from iron sources and coke layers formed from coke are alternately stacked. Then, the charged iron source is reduced by the reducing gas in the blast furnace and the carbon contained in the coke to obtain pig iron. Here, the coke has a function as a reducing agent for reducing the iron source, a function as a fuel, and a function as a spacer for ensuring voids for distributing gas throughout the furnace.

Stable operation in such blast furnaces is of great importance, as is cost reduction. For example, Patent Document 1 below describes a method for stably operating a blast furnace while suppressing an increase in pressure loss using inexpensive highly crystalline water ore, in which a hydrogen-containing substance is injected through the tuyeres as an auxiliary reducing agent. The method of operation is disclosed.

For example, in Patent Document 2, when operating a blast furnace in which a reducing agent with a high hydrogen content is injected, in order to ensure stable operation, synthetic oil above room temperature is installed in a stave that cools the furnace wall in the upper part of the furnace. , a blast furnace operating method is disclosed in which a temperature drop in the upper part of the furnace is suppressed by circulating mineral oil, coal-based tar, or combustion gas as a heat medium.

Japanese Patent Application Publication No. 2006-124769 Japanese Patent Application Publication No. 2009-221546

By the way, since coke is generally expensive, it is desired to reduce the manufacturing cost of pig iron by reducing the amount of coke used. However, when the amount of coke used is reduced, the spacer function of the coke is partially impaired, resulting in an increase in pressure loss within the furnace. When the pressure loss inside the furnace increases, the gas flow fluctuates, and, for example, a blow-through may occur in which gas flows unevenly to areas with good ventilation. This blow-through disturbs the stacked state of the ore layer and coke layer, reducing the reduction efficiency of the iron source. Furthermore, due to the increase in pressure loss, the reduction efficiency of the iron source by carbon monoxide gas decreases, and the temperature in the furnace decreases. When the temperature inside the furnace decreases, the efficiency of producing pig iron decreases. Furthermore, as the temperature inside the furnace decreases, the temperature of the hot metal decreases, the viscosity of the hot metal increases, and in some cases, it becomes impossible to tap the hot metal.

A method of operating a blast furnace that reduces pressure loss within the furnace while reducing the amount of coke used has not been sufficiently studied, and conventionally known methods cannot adequately address this problem. For example, in the blast furnace operating method described in Patent Document 1, since the reduction reaction using hydrogen is an endothermic reaction, the temperature inside the furnace may decrease. As a result, the relatively low temperature region in the upper part of the furnace may expand. In the low-temperature region, sintered ore, which is used as a type of iron source, is pulverized by a reduction reaction (reduction powdering), so as the low-temperature region in the upper part of the furnace expands, the area where sintered ore is reduced and pulverized increases. It turns out. As a result, in the upper part of the furnace, the gap may become smaller and pressure loss may increase. Furthermore, the area where the sintered ore is reduced and turned into powder is expanded, which may worsen the falling behavior of the iron source and coke.

In the blast furnace operating method described in Patent Document 2, since the degree of temperature rise in the upper part of the furnace is determined by heat conduction from the stave, a temperature distribution occurs in the radial direction of the furnace. Therefore, the amount of reduction and powdering of the sintered ore changes in the radial direction of the furnace. Changes in the amount of reduction and powdering of the sintered ore in the radial direction of the furnace may cause fluctuations in the gas flow, resulting in poor furnace conditions. Such problems become more pronounced in operations at low coke ratios. In addition, in the blast furnace operating method described in Patent Document 2, synthetic oil, mineral oil, coal-based tar, or combustion gas is used as a heat medium for the stave. There is a possibility that the heat medium may spout outside. Therefore, from the viewpoints of safety, environment, and disaster prevention, there is room for improvement in the above blast furnace operating method.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a method of operating a blast furnace that enables more stable and continuous operation under operating conditions of a low coke ratio, and to provide a method for operating a blast furnace and a method for operating a pig iron. The purpose of this invention is to provide a method for manufacturing the same.

(1) Operation of a blast furnace that produces pig iron by charging an iron source containing at least sintered ore and coke, and injecting pulverized coal and an auxiliary reducing agent containing at least either a gaseous reducing agent or a liquid reducing agent. A method,
The reduction pulverization index of the sintered ore is 24% or more and 34% or less,
The amount of pulverized coal used is 150 kg/tp or more and 220 kg/tp or less,
The amount of the auxiliary reducing agent used is 10 kg/tp or more and 50 kg/tp or less,
The method for operating a blast furnace, wherein the charging amount of the sintered ore is 70% by mass or more based on the mass of the iron source .
(2) The method for operating a blast furnace according to claim 1, wherein the amount of coke used is 300 kg/tp or less.
(3) By charging an iron source containing at least sintered ore and coke into a blast furnace, and blowing pulverized coal and an auxiliary reducing agent containing at least either a gaseous reducing agent or a liquid reducing agent into the blast furnace, A method for producing pig iron that obtains pig iron by reducing an iron source, the method comprising:
The reduction pulverization index of the sintered ore is 24% or more and 34% or less,
The amount of pulverized coal used is 150 kg/tp or more and 220 kg/tp or less,
The amount of the auxiliary reducing agent used is 10 kg/tp or more and 50 kg/tp or less,
A method for producing pig iron, wherein the charging amount of the sintered ore is 70% by mass or more based on the mass of the iron source .

According to the present invention, it is possible to provide a method for operating a blast furnace that allows more stable and continuous operation under operating conditions of a low coke ratio.

1 is a schematic diagram showing an example of a blast furnace to which a blast furnace operating method according to an embodiment of the present invention is applied. FIG. 2 is a graph diagram showing the relationship between the reduction pulverization index of sintered ore obtained through operational tests in Examples, the pressure loss in the lower part of the furnace, and the pressure loss in the upper part of the furnace.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that, in this specification and the drawings, components having substantially the same functional configurations are designated by the same reference numerals and redundant explanation will be omitted. Furthermore, the ratios and dimensions of each component in the drawings do not represent the actual ratios and dimensions of each component.

<1. Overview of blast furnace>
(1.1. Structure of blast furnace)
First, prior to explaining the blast furnace operating method and pig iron manufacturing method according to the present embodiment, a blast furnace to which the blast furnace operating method and pig iron manufacturing method according to the present embodiment are applied will be described with reference to FIG. . FIG. 1 is a schematic diagram showing an example of a blast furnace to which a method for operating a blast furnace and a method for manufacturing pig iron according to an embodiment of the present invention are applied.

The blast furnace 1 is a device that reduces iron source to produce hot metal. As shown in FIG. 1, the blast furnace 1 includes a furnace body 10, a tuyere 11, a blast main pipe 12, a blast pipe 13, a pulverized coal blowing lance 14, an auxiliary reducing agent blowing lance 15, a tap hole 16, and a slag tap hole 17. , and a rotating chute 18.

The furnace body 10 is a vertical reaction vessel with an open upper end. The furnace body 10 is formed of a hollow steel shell and a refractory material stretched on the inner surface of the steel shell. A reservoir 101 is provided below the furnace body 10 (hearth). An iron source and coke are charged into the furnace body 10 by various known methods through an opening at the upper end of the furnace body 10, and inside the furnace body 10, the iron source is reduced to produce hot metal. The generated hot metal is stored in the reservoir 101.

The tuyeres 11 are provided at the lower side of the side surface of the furnace body 10 and are blowing ports for blowing oxygen-containing hot air generated by a hot blast furnace (not shown) into the inside of the furnace body 10. The furnace body 10 can include a plurality of tuyeres 11. In addition to hot air, an auxiliary reducing agent and pulverized coal, which will be described later, can be blown into the furnace through the tuyeres 11.

The blast main pipe 12 is an annular pipe provided so as to surround the furnace body 10 , and the blast pipe 13 is connected to the blast main pipe 12 . The blast main pipe 12 supplies hot air sent from the hot air stove to the blast pipe 13.

The blow pipe 13 is connected to the blow main pipe 12 and the tuyere 11 . The blast pipe 13 supplies the hot air sent from the blast main pipe 12 into the furnace through the tuyeres 11.

Note that the temperature of the hot air supplied into the furnace is adjusted by controlling the amount of heat storage and the amount of hot air supplied in the hot blast furnace. Note that the content of oxygen contained in the hot air can be adjusted by mixing air and oxygen in the hot air stove.

The pulverized coal injection lance 14 has a tubular shape and supplies pulverized coal into the inside of the furnace body 10 through the tuyere 11 . The pulverized coal blowing lance 14 is inserted into the inside of the blast pipe 13 from the wall surface of the blast pipe 13, for example. Pulverized coal is blown into the furnace body 10 along with hot air.

The pulverized coal injection lance 14 is not particularly limited as long as a predetermined amount of pulverized coal is blown into the furnace, and for example, a circular tube, a square tube, a multiple tube in which tubes with different diameters are arranged concentrically, etc. can be used. be able to.

The auxiliary reducing agent injection lance 15 has a tubular shape and supplies an auxiliary reducing agent containing hydrogen into the interior of the furnace body 10 through the tuyere 11 . The auxiliary reducing agent blowing lance 15 is inserted into the inside of the blast pipe 13 from the wall surface of the blast pipe 13, for example.

The auxiliary reducing agent injected from the auxiliary reducing agent injection lance 15 is thermally decomposed in the furnace and becomes carbon monoxide gas, carbon dioxide gas, and hydrogen gas. Therefore, it is considered that the structure of the auxiliary reducing agent injection lance 15 or the method of injecting the auxiliary reducing agent has little influence on the gas flow in the furnace, the temperature change in the furnace, or the reduction reaction of the iron source. Therefore, the auxiliary reducing agent injection lance 15 is not particularly limited as long as a set amount of auxiliary reducing agent is blown into the furnace. Multiple tubes etc. can be used.

When the auxiliary reducing agent injection lance 15 is a single tube, the auxiliary reducing agent injection lance 15 can blow into the furnace an auxiliary reducing agent that is a mixture of a plurality of types of reducing agents. In addition, when the auxiliary reducing agent injection lance 15 is a multi-pipe lance, by supplying different reducing agents to each of the plurality of spaces formed inside the auxiliary reducing agent injection lance 15, multiple types of auxiliary reduction can be performed. Both materials can be blown into the furnace at the same time.

The tap hole 16 is provided in the reservoir 101 and taps hot metal generated by reduction of the iron source. A plurality of tap holes 16 are provided, and hot metal can be tapped continuously or intermittently.

The slag tap port 17 is provided above the tap port 16 of the hearth. Slag generated by reduction of the iron source is discharged from the slag outlet 17. A plurality of slag outlets 17 are provided, and the slag can be continuously or intermittently extracted.

The rotating chute 18 is provided above the furnace body 10 and charges iron source and coke into the inside of the furnace body 10. The iron source and coke are charged into a desired position in a desired furnace by controlling the inclination angle and rotation speed of the rotating chute 18.

(1.2. Condition inside the furnace)
Next, the situation inside the furnace body 10 during the reduction reaction will be explained. In the blast furnace 1 in operation, an iron source and coke are charged into the furnace body 10 from the top of the furnace, and hot air containing oxygen, pulverized coal, and an auxiliary reducing agent are blown into the furnace body 10 from the tuyeres 11. The oxygen in the hot air burns the coke, pulverized coal, and auxiliary reducing material, producing reducing gases including carbon monoxide and hydrogen gas. The generated reducing gas reduces Fe ₂ O ₃ , Fe ₃ O ₄ , etc. contained in the iron source, and hot metal containing about 4.5% carbon is generated. Inside the furnace body 10 in which pig iron is produced in this way, there is a lumpy zone 20, a cohesive zone 30 formed below the cohesive zone 20, and a dripping zone 40 formed below the cohesive zone 30. is formed.

The lumpy zone 20 is formed by alternately charging iron sources and coke using the rotating chute 18, so that ore layers 201 made of iron sources and coke layers 202 made of coke are stacked alternately. This is the area formed by The lumpy zone 20 is formed, for example, by alternately charging an iron source and coke from the top of the furnace body 10 through a rotating chute 18 . A block zone 20 is formed in the upper part of the furnace, as shown in FIG. In the block zone 20, the iron source is reduced by the reducing gas rising from below the blast furnace. The reduction reaction of the iron source in the massive zone 20 starts at around 500°C and is reduced to FeO at around 900°C to 1000°C. In the relatively low temperature region of the lumpy zone 20, the sintered ore may be reduced and powdered.

The cohesive zone 30 is a region where reduction of the iron source existing below the lumpy zone 20 progresses, and the solid iron source and the once molten iron source are fused and exist in a semi-molten state. In the cohesive zone 30, the iron source is reduced by reducing gas and carbon contained in coke or pulverized coal. In the cohesive zone 30, for example, FeO generated during the reduction of the iron source reacts with the slag component, resulting in a semi-molten state. Between the plurality of cohesive zones 30, there is a coke layer (coke slit 50) that is a flow path for gas to move from the drip zone 40 to the lump zone 20. The reducing gas in the lower part of the furnace moves to the lump zone 20 through the coke slit 50.

The dripping zone 40 is mainly formed of coke, and is a region where hot metal and molten slag drip downward through the gaps between the cokes. Hot metal and molten slag are stored in a reservoir 101.

The blast furnace 1 and the situation inside the furnace have been described above. As described above, in the operation of the blast furnace 1, the coke functions as a flow path for the reducing gas. Therefore, under operating conditions of a low coke ratio, the number of flow paths for the reducing gas decreases, making pressure loss more likely to occur. However, in the blast furnace operating method and pig iron manufacturing method according to the present embodiment, which will be described later, the amounts of pulverized coal and auxiliary reducing agent are set within a specific range, and sintered ore with a predetermined reduction pulverization index is used. Even when operating conditions with a low coke ratio are adopted, pressure loss is suppressed and stable blast furnace operation is possible.

<2. Blast furnace operating method and pig iron manufacturing method>
Next, a method for operating a blast furnace and a method for manufacturing pig iron according to the present embodiment will be explained. In addition, in the following explanation, the blast furnace operating method and the pig iron manufacturing method according to the present embodiment will be explained using the blast furnace 1, but the blast furnace operating method and the pig iron manufacturing method according to the present embodiment are applied. It goes without saying that the blast furnace is not limited to the blast furnace 1 described above.

The blast furnace operating method according to the present embodiment includes charging an iron source containing at least sintered ore and coke, and blowing pulverized coal and an auxiliary reducing agent containing at least either a gaseous reducing agent or a liquid reducing agent. This is a method of manufacturing pig iron. In the same method, the reduction pulverization index of the sintered ore is 24% or more and 34% or less, the amount of pulverized coal used is 150 kg/tp or more and 220 kg/tp or less, and the amount of auxiliary reducing material used is , 10 kg/tp or more and 50 kg/tp or less. Moreover, the method for manufacturing pig iron according to the present embodiment is a method for obtaining pig iron by the above-described blast furnace operating method.

In this embodiment, the iron source and coke are alternately charged using the rotating chute 18. Further, the pulverized coal and the auxiliary reducing agent are supplied into the furnace body 10 through the tuyere 11 from the pulverized coal injection lance 14 and the auxiliary reducing agent injection lance 15, respectively. By keeping the amounts of pulverized coal and auxiliary reducing agent within the above-mentioned range and using the specified sintered ore as an iron source, stable blast furnace operation is achieved even under operating conditions of low coke ratio. do. Each of these materials will be explained below.

(2.1. Iron source)
The iron source for producing pig iron using the blast furnace 1 includes at least sintered ore. Sintered ore is obtained by mixing coke and limestone with powdered ore and sintering the mixture.

In this embodiment, the sintered ore used has a reduction disintegration index (RDI) of 24 to 34%. RDI is an index indicating the degree of pulverization of iron ore under conditions simulating the low-temperature reduction zone of a blast furnace. When the RDI is less than 24%, the reducibility (RI: Reduction index) of the sintered ore becomes small, and reduction of the sintered ore by the reducing gas inside the furnace body 10 is suppressed. Therefore, the thickness of the cohesive zone 30 becomes thicker, and the pressure loss of the gas increases in the lower part of the furnace.As a result, the situation inside the furnace fluctuates and the operation becomes unstable. On the other hand, if the RDI exceeds 34%, the sintered ore will be pulverized in the upper part of the furnace, the gas pressure loss in the upper part of the furnace will increase, the stacked state of the lumpy zone 20 will be disturbed, and the reduction efficiency of the iron source may decrease. There is sex. The RDI of the sintered ore is preferably 24% or more and 32% or less.

RDI can be evaluated, for example, by a method based on JIS 8720:2009 Iron ore - Low temperature reduction powdering test method. Specifically, sintered ore having a predetermined particle size is left standing and subjected to isothermal reduction using a gas composed of carbon monoxide and nitrogen at a temperature of 550° C. for 30 minutes. The sintered ore after reduction is cooled to a temperature of 100° C. or lower, and rotated a total of 900 times using a predetermined rotating drum. Thereafter, sieving is performed using a sieve with a nominal opening of 2.8 mm. RDI is expressed as the mass of the sintered ore passing through the sieve relative to the mass of the sintered ore before the reduction reaction.

The RDI of sintered ore can be adjusted using a known method. RDI can be adjusted, for example, by changing the amount of coke powder when producing sintered ore by mixing and firing ore powder, coke powder, and limestone.

The RI of the sintered ore is not particularly limited, but is, for example, 64% or more and 69% or less, preferably 66% or more and 69% or less. By using sintered ore having an RI in the above range, it is possible to maintain the reducibility of the sintered ore by the reducing gas inside the furnace body 10 while suppressing an increase in pressure loss due to pulverization of the sintered ore. becomes possible.

RI can be evaluated, for example, by a method based on JIS 8713:2009 Iron ore - Reducibility test method. Specifically, a measurement sample placed in a container and suspended on a balance is subjected to isothermal reduction using a mixed gas of carbon monoxide and nitrogen at a temperature of 900° C. for 180 minutes. RI is determined as the ratio of the mass of oxygen removed by reduction to the mass of oxygen bound to iron in the measurement sample before reduction.

Further, the average particle size of the sintered ore is preferably 18 mm or more and 25 mm or less. By using sintered ore having an average particle size within the above range, it is possible to reduce the influence of pressure loss due to reduction powdering and to enhance the hydrogen gas reduction effect accompanying the injection of the auxiliary reducing agent.

The composition of the sintered ore is T. It is preferable that Fe (iron content) is high. By using the sintered ore having the above composition, it is possible to enhance the hydrogen gas reduction effect accompanying the injection of the auxiliary reducing agent.

The amount of sinter charged is preferably 70% by mass or more based on the mass of the iron source to be charged. By setting the charging amount of sinter to 70% by mass or more based on the mass of the iron source to be charged, the reducing ability of the entire iron source to be charged can be maintained. The reduction effect of hydrogen gas accompanying this can be enhanced.

Moreover, in this embodiment, the iron source may further include pellets obtained by granulating lump ore, which is a lump-like iron ore, and/or powder ore.

(2.2. Reducing material)
As described above, in this embodiment, coke, pulverized coal, and an auxiliary reducing agent are used as reducing agents. The reducing agent is decomposed by thermal decomposition within the furnace body 10 to generate carbon monoxide gas and hydrogen gas. Then, the iron source is reduced by these carbon monoxide gas and hydrogen gas.

The Reduction Agent Ratio (RAR), which is the amount of reducing agent used per ton of pig iron production, is the coke ratio (CR) and the amount of pulverized coal used per ton of pig iron production. It can be the total amount of the pulverized coal ratio (PCR) and the usage amount of the auxiliary reducing agent. The reducing agent ratio can be changed as appropriate depending on the properties of the iron source, the properties of coke, the properties of pulverized coal, the type of auxiliary reducing agent, the blast furnace equipment, etc., but the reducing agent ratio is, for example, 500 kg. It is preferable to set it within the range of ±2% based on /tp. Each reducing agent will be explained below.

[2.2.1. Coke]
In this embodiment, the coke ratio is not particularly limited, and can be used in any range, for example, from 230 kg/tp to 350 kg/tp. However, in this embodiment, the coke ratio is preferably 300 kg/tp or less. By setting the coke ratio to 300 kg/tp or less, it is possible to reduce the manufacturing cost of pig iron. Generally, when the coke ratio decreases, the thickness of the coke layer with a relatively high porosity decreases, resulting in a decrease in air permeability and an increase in the pressure loss of the gas in the furnace. When the amount of coke charged is reduced, for example, in the cohesive zone 30, the coke slit 50 becomes narrower, so pressure loss may increase. However, in the blast furnace operating method according to the present embodiment, the RDI of the sintered ore is 24% or more and 34% or less, the pulverized coal ratio is 150 kg/tp or more and 220 kg/tp or less, and the amount of auxiliary reducing material used is 10 kg. /tp or more and 50 kg/tp or less, it becomes possible to stably operate the blast furnace even if the coke ratio is 300 kg/tp or less. Preferably, the coke ratio is 230 kg/tp or more and 300 kg/tp or less.

Further, preferably, the average particle size of the coke is 40 mm or more and 60 mm or less. By using coke having an average particle size within the above range, it becomes possible to more effectively distribute gas throughout the furnace.

[2.2.2. Pulverized coal]
The pulverized coal ratio is 150 kg/tp or more and 220 kg/tp or less. By injecting pulverized coal within this range into the furnace, the generation of unburned char is suppressed while reducing the coke ratio. If the pulverized coal ratio is less than 150 kg/tp, it will be necessary to increase the coke ratio to reduce the charged iron source. When the pulverized coal ratio exceeds 220 kg/tp, unburned char increases, pressure loss increases, and furnace conditions deteriorate. The pulverized coal ratio is preferably 190 kg/tp or more and 220 kg/tp or less. By injecting pulverized coal within this range into the furnace, the coke ratio can be made 300 kg/tp or less by injecting the auxiliary reducing agent at a minimum of 10 kg/tp. The size of the pulverized coal is not particularly limited as long as it can be blown into the furnace through the tuyere 11 using the pulverized coal injection lance 14.

[2.2.3. Auxiliary reducing agent]
As the auxiliary reducing agent, at least either a gaseous reducing agent or a liquid reducing agent is used. The auxiliary reducing agent is blown into the furnace body 10 along with the hot air. As shown in Table 1, for example, a substance containing hydrogen atoms as a constituent atom is used as the auxiliary reducing agent, and it is preferable to use a substance that does not generate ash. For example, it is preferable to use a material containing hydrocarbon as the auxiliary reducing material. As the gaseous reducing agent, for example, natural gas or city gas containing methane, ethane, propane, etc., coke oven gas containing hydrogen and methane, coal gasified gas containing a large amount of carbon monoxide and hydrogen, etc. can be used. can. Further, hydrogen gas can also be used as the gaseous reducing agent. As the liquid reducing agent, for example, heavy oil, tar, etc. can be used.

The amount of auxiliary reducing agent used shall be 10 kg/tp or more and 50 kg/tp or less. By injecting the auxiliary reducing agent in this range into the furnace, hydrogen gas generated by decomposition of the auxiliary reducing agent is used to reduce the iron source, so that the cohesive zone 30 becomes thinner. As a result, the increase in pressure loss in the lower part of the furnace is suppressed. If the amount of the auxiliary reducing agent used is less than 10 kg/tp, the reduction of the iron source by the auxiliary reducing agent is not promoted, so the cohesive zone 30 is not made thinner, and the pressure loss of the gas in the lower part of the furnace is reduced. I can't. When the amount of auxiliary reducing material used is more than 50 kg/tp and the pulverized coal ratio described below is 150 kg/tp or more, if the auxiliary reducing material contains a large amount of hydrocarbons, oxygen in the furnace will preferentially interact with hydrocarbons. react. Therefore, so-called unburned char, which is the unburned remains of the pulverized coal, is generated, and this unburned char remains in the furnace. Due to the accumulation of unburned char in the furnace, the gas pressure loss in the lower part of the furnace increases, leading to poor furnace conditions. The amount of the auxiliary reducing agent used is preferably 20 kg/tp or more and 40 kg/tp or less. By injecting the auxiliary reducing agent within this range into the furnace, the combustion efficiency of pulverized coal can be improved.

Hydrogen gas that contributes to the reduction of the iron source is generated by the thermal decomposition of the auxiliary reducing agent and the thermal decomposition of the moisture inside the furnace body 10. The amount of hydrogen gas inside the furnace body 10 is preferably 10 kg/tp or more and 22 kg/tp or less per ton of pig iron produced. Hydrogen reduces iron sources at a higher rate than carbon monoxide. Therefore, by introducing 10 kg/tp or more of hydrogen into the furnace, relatively low melting point FeO produced in the reduction process of the iron source is reduced. As a result, the upper end of the cohesive zone 30 shifts to the high temperature region (in other words, below the furnace), so the region where the cohesive zone 30 exists becomes narrower. Therefore, by introducing 10 kg/tp or more of hydrogen into the furnace, it is possible to suppress the increase in pressure loss in the lower part of the furnace. By setting the amount of hydrogen gas inside the furnace body 10 to 22 kg/tp or less, it is possible to suppress the expansion of the reduction and powdering region of the sintered ore, and it is possible to suppress the increase in pressure loss in the upper part of the furnace. Become. Note that when hydrogen gas is blown in as an auxiliary reducing agent, the hydrogen gas is included in the hydrogen gas inside the furnace body 10.

As described above, according to the method of operating a blast furnace and the method of manufacturing pig iron according to the present embodiment described above, more stable and continuous operation is possible under operating conditions of a low coke ratio.

Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that the embodiments described below are merely examples of the present invention, and do not limit the present invention.

An operational test was conducted on a blast furnace with an internal volume of 5000m class ³ . The operational test was conducted under the conditions shown in Table 2. In this operational test, sintered ore, lump ore, and pellets were used as iron sources. The average particle size of the sintered ore was 20 mm, the average particle size of the lump ore was 23 mm, and the average particle size of the pellets was 18 mm. The proportions of sintered ore, lump ore, and pellets used in the operational test were 75% by mass, 15% by mass, and 10% by mass, respectively. Further, the RDI of the sintered ore was adjusted by changing the amount of coke breeze used when producing the sintered ore. In addition, city gas was used as an auxiliary reducing agent. Elemental analysis of the city gas used in the operational test revealed that the city gas contained 75.9% by mass of C and 24.1% by mass of H. Pulverized coal and city gas were each blown into the furnace through the tuyere using a single-tube blowing lance.

In Table 2, the oxygen enrichment rate indicates the difference between the oxygen concentration in the hot air blown into the blast furnace from the hot blast furnace and the oxygen concentration in the atmosphere. The oxygen enrichment rate was 4.8% in the standard operation example, 10.5% in Comparative Example 1, and 20.0% in Comparative Examples 2 to 5 and Examples 1 to 6.

RDI was evaluated based on JIS 8720:2009 Iron ore - Low temperature reduction powdering test method. Further, RI was evaluated based on JIS 8713:2009 Iron ore - Reducibility test method.

The operational stability was evaluated by measuring the gas pressure loss in the upper part of the furnace and the gas pressure loss in the lower part of the furnace. In detail, if the pressure loss in the upper part of the furnace and the stable pressure loss in the lower part of the furnace can be measured, the operational stability is considered good (○), and the pressure loss in the upper part of the furnace or the pressure loss in the lower part of the furnace is unstable and fluctuates. In this case, the operational stability was rated as poor (×). The above are shown in Table 2.

First, as a standard operation example, a blast furnace was operated using sintered ore with an RDI of 38%, PCR at 200 kg/tp, RAR at 500 kg/tp, and CR at 300 kg/tp. In the standard operation example, no auxiliary reducing agent was injected. In the standard operation example, the pressure loss in the upper part of the furnace and the pressure loss in the lower part of the furnace were 40.8 kPa and 73.5 kPa, respectively, and the operational stability was good.

In Comparative Example 1, sintered ore with an RDI of 38% was used, the PCR was increased from 200 kg/tp used in the standard operation example to 250 kg/tp, and the CR was increased from 300 kg/tp used in the standard operation example to 250 kg/tp. The blast furnace was operated after reducing the amount to tp. In Comparative Example 1, as in the standard operation example, no auxiliary reducing agent was injected. In Comparative Example 1, the pressure loss in the upper part of the furnace was 46.3 kPa, but the pressure loss value fluctuated in the lower part of the furnace, resulting in poor operational stability. In Comparative Example 1, this is considered to be because the width of the coke slit in the cohesive zone became narrower due to the CR being reduced to 250 kg/tp.

In Comparative Example 2, sintered ore with RDI of 38% was used, PCR was 220 kg/tp, city gas consumption was 50 kg/tp, and CR was reduced from 300 kg/tp used in the standard operation example to 230 kg/tp. and operated the blast furnace. Since city gas was blown into the furnace, the amount of hydrogen gas (InputH ₂ ) in the furnace was 11.8 kg/tp. In Comparative Example 2, the pressure loss in the lower part of the furnace was 77.1 kPa, but the pressure loss value fluctuated in the upper part of the furnace, resulting in poor operational stability. In Comparative Example 2, reduction of the iron source was promoted by hydrogen gas derived from city gas, and the area where the cohesive zone existed became narrower, so it is thought that no fluctuation in pressure loss occurred in the lower part of the furnace. On the other hand, it is considered that the increase in Input H ₂ promoted the reduction and pulverization of the sintered ore in the upper part of the furnace, causing the pressure loss to fluctuate.

In Comparative Example 3, sintered ore with an RDI of 36% was used, and the operation was carried out with PCR at 220 kg/tp, city gas consumption at 50 kg/tp, and CR at 230 kg/tp. In Comparative Example 3, the pressure loss in the lower part of the furnace was 78.2 kPa, but the pressure loss value fluctuated in the upper part of the furnace, resulting in poor operational stability. Even when sintered ore with an RDI of 36% was used, the reduction of the iron source was promoted by hydrogen gas derived from city gas, and the area where the cohesive zone existed became narrower, resulting in fluctuations in pressure loss in the lower part of the furnace. It is thought that there was no such thing. On the other hand, even if the RDI of the sintered ore was 36%, the reduction and pulverization of the sintered ore was promoted in the upper part of the furnace, so it is thought that the pressure loss in the upper part of the furnace increased.

Examples 1 to 6, Comparative Example 4, and Comparative Example 5 are operational test examples in which the RDI of the sintered ore in Comparative Example 3 was changed. Specifically, as shown in Table 2, in all of Examples 1 to 6, Comparative Example 4, and Comparative Example 5, PCR was 220 kg/tp, city gas consumption was 50 kg/tp, and CR was 230 kg/tp. It was set as tp. In addition, the RDI of the sintered ore was 34% in Example 1, 32% in Example 2, 30% in Example 3, 28% in Example 4, 26% in Example 5, and 24% in Example 6. In Comparative Example 4, it was 22%, and in Comparative Example 5, it was 20%. In Example 7, PCR was 200 kg/tp, city gas usage was 50 kg/tp, CR was 250 kg/tp, and RDI of sintered ore was 24%.

In Example 1, the pressure loss in the upper part of the furnace and the pressure loss in the lower part of the furnace were 47.8 kPa and 79.8 kPa, respectively, and the operational stability was good. In Example 2, the pressure loss in the upper part of the furnace and the pressure loss in the lower part of the furnace were 45.1 kPa and 81.5 kPa, respectively, and the operational stability was good. In Example 3, the pressure loss in the upper part of the furnace and the pressure loss in the lower part of the furnace were 42.3 kPa and 83.5 kPa, respectively, and the operational stability was good. In Example 4, the pressure loss in the upper part of the furnace and the pressure loss in the lower part of the furnace were 40.2 kPa and 85.7 kPa, respectively, and the operational stability was good. In Example 5, the pressure loss in the upper part of the furnace and the pressure loss in the lower part of the furnace were 38.5 kPa and 88.8 kPa, respectively, and the operational stability was good. In Example 6, the pressure loss in the upper part of the furnace and the pressure loss in the lower part of the furnace were 36.5 kPa and 91.5 kPa, respectively, and the operational stability was good. In Examples 1 to 6, by using sintered ore with a low RDI, the reduction and powdering of the sintered ore in the upper part of the furnace is suppressed to the extent that stable operation of the blast furnace is possible, while reducing the amount of sintered ore derived from the auxiliary reducing agent. It is thought that hydrogen gas promoted the reduction of the iron source and narrowed the cohesive zone, resulting in good operational stability.

In Comparative Example 4, the pressure loss in the upper part of the furnace was 35.2 kPa, but the pressure loss value fluctuated in the lower part of the furnace, resulting in poor operational stability. In Comparative Example 5, the pressure loss in the upper part of the furnace was 34.0 kPa, but the pressure loss value fluctuated in the lower part of the furnace, resulting in poor operational stability. In Comparative Examples 4 and 5, reduction and powdering of the sintered ore was suppressed, so it is thought that the pressure loss in the upper part of the furnace was reduced. On the other hand, the RDI of the sintered ore used in Comparative Example 4 and Comparative Example 5 was 22% and 20%, respectively, and the sintered ore having an RDI smaller than the RDI of the sintered ore used in Example 6 was used. . As a result, in Comparative Examples 4 and 5, the RI of the sintered ore became smaller as the RDI decreased, so the reduction of the sintered ore by hydrogen gas was suppressed, the pressure loss in the lower part of the furnace increased, and the operation was interrupted. It is thought that the situation has become stable.

In Example 7, the pressure loss in the upper part of the furnace and the pressure loss in the lower part of the furnace were 34.9 kPa and 89.4 kPa, respectively, and the operational stability was good. In Example 7, by using sintered ore with an RDI of 24%, the reduction and pulverization of the sintered ore in the upper part of the furnace is suppressed to the extent that stable operation of the blast furnace is possible, while the hydrogen gas derived from the auxiliary reducing agent is suppressed. It is thought that this facilitated the reduction of the iron source and narrowed the cohesive zone, resulting in good operational stability.

FIG. 2 shows the relationship between the RDI of sintered ore obtained in the operational test, the pressure loss in the upper part of the furnace, and the pressure loss in the lower part of the furnace. FIG. 2 is a plot of the pressure loss in the upper part of the furnace and the pressure loss in the lower part of the furnace in Examples 1 to 6 and Comparative Examples 1 to 4.

As shown in FIG. 2, as the RDI of the sintered ore decreased, the pressure loss in the lower part of the furnace increased, and when the RDI was less than 24%, the furnace condition became poor. Moreover, as the RDI of the sintered ore increased, the pressure loss at the upper part of the furnace increased, and when the RDI of the sintered ore was greater than 34%, the furnace condition became poor. It was found that it is possible to stably operate a blast furnace when the RDI of sintered ore is in the range of 24% or more and 34% or less.

As explained above, according to the present invention, it is possible to operate the blast furnace more stably and continuously under operating conditions of a low coke ratio.

Although preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea stated in the claims. It is understood that these also naturally fall within the technical scope of the present invention.

1 Blast furnace 10 Furnace body 11 Tuyere 12 Main blast pipe 13 Blast pipe 14 Pulverized coal blowing lance 15 Auxiliary reducing agent blowing lance 16 Tapping port 17 Slag tap port 18 Rotating chute 20 Clumping zone 30 Cohesive zone 40 Dripping zone 50 Coke slit 101 Reservoir 201 Ore layer 202 Coke layer

Claims (3)

A blast furnace operating method for producing pig iron by charging an iron source containing at least sintered ore and coke, and injecting pulverized coal and an auxiliary reducing agent containing at least either a gaseous reducing agent or a liquid reducing agent. hand,
The reduction pulverization index of the sintered ore is 24% or more and 34% or less,
The amount of pulverized coal used is 150 kg/tp or more and 220 kg/tp or less,
The amount of the auxiliary reducing agent used is 10 kg/tp or more and 50 kg/tp or less,
The method for operating a blast furnace, wherein the charging amount of the sintered ore is 70% by mass or more based on the mass of the iron source . The method of operating a blast furnace according to claim 1, wherein the amount of coke used is 300 kg/tp or less. The iron source is reduced by charging an iron source containing at least sintered ore and coke into a blast furnace, and blowing pulverized coal and an auxiliary reducing agent containing at least either a gaseous reducing agent or a liquid reducing agent into the blast furnace. A method for producing pig iron that obtains pig iron by reduction,
The reduction pulverization index of the sintered ore is 24% or more and 34% or less,
The amount of pulverized coal used is 150 kg/tp or more and 220 kg/tp or less,
The amount of the auxiliary reducing agent used is 10 kg/tp or more and 50 kg/tp or less,
A method for producing pig iron, wherein the charging amount of the sintered ore is 70% by mass or more based on the mass of the iron source .

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