WO2018180892A1

WO2018180892A1 - Method for operating blast furnace

Info

Publication number: WO2018180892A1
Application number: PCT/JP2018/011417
Authority: WO
Inventors: 尚貴山本; 明紀村尾; 裕之堀越; 亮丞宮越; 晃太盛家; 深田　喜代志
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2017-03-30
Filing date: 2018-03-22
Publication date: 2018-10-04

Abstract

Provided is a method for operating a blast furnace in which hot air is supplied from a hot air pipe to the inside of a blowpipe the tip of which is connected to a tuyere of a blast furnace, the hot air is supplied to the inside of the blast furnace from the tuyere via the inside of the blowpipe, a first solid reducing agent is blown from an inside pipe of a first double pipe lance the tip of which is inserted into the inside of the blowpipe and a combustion supporting gas is blown from an outside pipe of the first double pipe lance simultaneously to the inside of the blowpipe so as to supply the same to the inside of the furnace from the tuyere, and a second solid reducing agent is blown from an inside pipe of a second double pipe lance the tip of which is inserted into the inside of the blowpipe and an easily combustible reducing gas is blown from an outside pipe of the second double pipe lance simultaneously to the inside of the blowpipe so as to supply the same to the inside of the furnace from the tuyere, wherein the method is characterized in that index A for blow-in of the combustion supporting gas defined by Equation (1) is set at 100 – 100,000, and index B for blow-in of the easily combustible reducing gas defined by Equation (2) is set at 300 – 100,000. A = V1 × F1 ... (1), B = V2 × F2 ... (2)

Description

Blast furnace operation method

In the blast furnace operation in which a solid fuel such as pulverized coal is injected simultaneously with a flammable gas such as oxygen and / or a flammable reducing gas such as city gas at the blast furnace tuyere, By adjusting the flow rate of the flammable reducing gas, the temperature rise and the flammability around the solid fuel are improved, thereby reducing the coke ratio and reducing material ratio in blast furnace operation.

In recent years, global warming associated with an increase in carbon dioxide emissions has become a problem, and the suppression of emitted CO ₂ is an important issue even in the steel industry. In response to this, in recent blast furnace operations, the ratio of reducing agent rate (RAR: Abbreviation for Reduction Agent Rate) is the total amount of reducing material injected from the tuyere and coke charged from the top of the furnace per 1 ton of pig iron. ) Is strongly promoted.

In blast furnace operation, mainly coke and pulverized coal blown from the tuyere are used as reducing materials. In such blast furnace operation, in order to reduce the ratio of reducing materials and to suppress the discharge of carbon dioxide, there is a policy to replace coke with reducing materials with high hydrogen content such as waste plastic, city gas, and heavy oil. It is valid.

For example, in Patent Document 1, a mixed reducing material mixed with a solid reducing material and a flammable reducing material and a combustion-supporting gas are mixed from a double-pipe lance whose tip is inserted into a blow pipe that is a hot air flow path. Blast furnace operation method that cools by blowing from the inner pipe and the outer pipe to improve combustibility and regulates the outlet flow velocity in the outer pipe to 20 to 120 m / s so that the double pipe lance is not deformed by heat. is doing.

In Patent Document 2, the amount of pulverized coal and the amount of gaseous fuel that are blown from the same tuyere are blown with a specific relational expression to improve combustibility and suppress the generation of unburned char. A blast furnace operating method consisting of the following has been proposed.

Further, in Patent Document 3, when low volatile pulverized coal having an average volatile content of 25 mass% or less is used, the oxygen concentration in the gas blown simultaneously with the pulverized coal is set to 70 vol% in the vicinity of the tip of the pulverized coal blowing lance. A method for improving the combustibility of low-volatile matter pulverized coal in a blast furnace has been proposed, which is ensured as described above or the oxygen concentration in the pulverized coal carrier gas is set to 70 vol% or more.

Japanese Patent No. 5699834 Japanese Patent No. 4714544 Japanese Patent No. 4074467

The blast furnace operation methods described in Patent Documents 1 and 2 are effective in improving the combustion temperature of pulverized coal and reducing the basic unit of reducing material compared to the conventional method of blowing only pulverized coal from the tuyere. However, there were problems as described below.

In the blast furnace operation method described in Patent Document 1, cooling of the lance is considered only by the gas flow rate. However, since the gas flow rate also affects the cooling, it is necessary to consider cooling from both the gas flow rate and the gas flow rate. .
Moreover, no consideration is given to the influence of the gas flow rate on the combustibility of pulverized coal, leaving room for further improvement.

The blast furnace operating method described in Patent Document 2 has a problem in that the positions where pulverized coal and city gas are blown are unclear.
In addition, the respective contact properties of pulverized coal, city gas, and oxygen during blowing affect the flammability of pulverized coal, but no particular consideration is given to this point.

In the blast furnace operating method described in Patent Document 3, the oxygen concentration in the gas blown simultaneously with the pulverized coal is controlled to be a certain level or more, but even if the oxygen concentration around the pulverized coal particles is increased, If the temperature cannot be raised to the temperature at which the pulverized coal particles ignite, the combustion reaction will not occur. Therefore, in the combustion of pulverized coal particles, there is a problem that not only the oxygen concentration but also the temperature rise of the pulverized coal particles must be improved at the same time.

The present invention has been developed to solve the above-described current situation.
First, in the present invention, when the solid reducing material is blown from the tuyere through the double pipe lance, two double pipe lances are used. A solid reducing material is injected from the other double pipe lance with a flammable reducing gas and a solid reducing material, respectively.
Further, in the present invention, when the solid reducing material is blown from the tuyere through the double tube lance, one double tube lance is used, and the combustion supporting gas and the solid reducing material are supplied from the double tube lance. Infuse.
Further, in the present invention, when the solid reducing material is blown from the tuyere through the double pipe lance, only one double pipe lance is used, and the flammable reducing gas is emitted from the double pipe lance. And blow in solid reducing material.

And in any case, by adding not only the flow rate but also the flow rate of the combustion-supporting gas and the flammable reducing gas to be injected, the mixing of pulverized coal and oxygen in the blowing gas is improved, Therefore, by improving the reactivity between pulverized coal and oxygen, not only the improvement of combustibility but also the reduction of the reducing material basic unit can be achieved.

That is, the gist configuration of the present invention is as follows.
1. Supplying hot air from the hot air pipe to the inside of the blow pipe whose tip is connected to the tuyere of the blast furnace, supplying the hot air from the tuyere into the furnace via the inside of the blow pipe,
A first solid reducing material is blown from the inner pipe of the first double pipe lance whose tip is inserted into the blow pipe, and a combustion-supporting gas is blown into the blow pipe simultaneously from the outer pipe. Then, supply from the tuyere into the furnace,
A second solid reducing material is introduced from the inner pipe of the second double pipe lance having a tip inserted into the blow pipe, and a flammable reducing gas is introduced from the outer pipe to the inside of the blow pipe. A blast furnace operating method that is simultaneously blown and supplied into the furnace from the tuyere,
The combustion support gas injection index A defined by the following formula (1) is set to 100 or more and 100000 or less, and the combustion index of the flammable reducing gas defined by the following formula (2) A method of operating a blast furnace, characterized in that B is 300 to 100000.
A = V ₁ × F ₁ (1)
B = V ₂ × F ₂ (2)
here,
V ₁ : Corrected gas flow velocity (m / s) of the combustion-supporting gas at the tip of the first double pipe lance, calculated by the following equation (3)
F ₁ : Gas flow rate of combustion-supporting gas per lance (Nm ³ / h)
V ₂ : Corrected gas flow rate (m / s) of the flammable reducing gas at the tip of the second double pipe lance, calculated by the following equation (4)
F ₂ : Gas flow rate of flammable reducing gas per lance (Nm ³ / h)
And
_{_{V 1 = {(G 1/}} 3600) × (T 1 /273.15)×(P A / P B)} / S 1 ··· (3)
_{_{V 2 = {(G 2/}} 3600) × (T 2 /273.15)×(P A / P B)} / S 2 ··· (4)
In
G ₁ : Gas flow rate of the combustion-supporting gas in the standard state (Nm ³ / h)
G ₂ : Gas flow rate of flammable reducing gas in standard state (Nm ³ / h)
T ₁ : Temperature of supporting gas (K)
T ₂ : temperature of the flammable reducing gas (K)
P _A : Atmospheric pressure (kPa)
P _B : Hot air blowing pressure (kPa)
S ₁ : Cross-sectional area of the combustion-supporting gas in the first double-pipe lance (m ² )
S ₂ : Cross-sectional area of the flammable reducing gas in the second double-pipe lance (m ² )
It is.

2. The blast furnace operating method according to 1, wherein the combustion-supporting gas is oxygen.

3. The blast furnace operating method according to 1 or 2, wherein the combustion-supporting gas is blown in a range of 9 kg to 370 kg per 1 ton of pig iron.

4). Any of the above 1-3, wherein the flammable reducing gas is one or more selected from city gas, natural gas, propane gas, hydrogen, converter gas, blast furnace gas, and coke oven gas The blast furnace operating method according to one item.

5. The blast furnace operating method according to any one of claims 1 to 4, wherein the flammable reducing gas is blown in a range of 0.1 kg to 50 kg per ton of pig iron.

6). Supplying hot air from the hot air pipe to the inside of the blow pipe whose tip is connected to the tuyere of the blast furnace, supplying the hot air from the tuyere into the furnace via the inside of the blow pipe,
A first solid reducing material is blown from the inner pipe of the first double pipe lance whose tip is inserted into the blow pipe, and a combustion-supporting gas is blown into the blow pipe simultaneously from the outer pipe. In the blast furnace operating method of supplying into the furnace from the tuyere,
A method for operating a blast furnace, characterized in that an injection index A of the combustion-supporting gas defined by the following formula (1) is 100 or more and 100000 or less.
A = V ₁ × F ₁ (1)
here,
V ₁ : Corrected gas flow velocity (m / s) of the combustion-supporting gas at the tip of the first double pipe lance, calculated by the following equation (3)
F ₁ : Gas flow rate of combustion-supporting gas per lance (Nm ³ / h)
And
_{_{V 1 = {(G 1/}} 3600) × (T 1 /273.15)×(P A / P B)} / S 1 ··· (3)
In
G ₁ : Gas flow rate of the combustion-supporting gas in the standard state (Nm ³ / h)
T ₁ : Temperature of supporting gas (K)
P _A : Atmospheric pressure (kPa)
P _B : Hot air blowing pressure (kPa)
S ₁ : Cross-sectional area of the combustion-supporting gas in the first double-pipe lance (m ² )
It is.

7). The blast furnace operating method according to the above 6, wherein the combustion-supporting gas is oxygen.

8). The blast furnace operating method according to 6 or 7, wherein the combustion-supporting gas is blown in a range of 9 kg to 370 kg per 1 ton of pig iron.

9. Supplying hot air from the hot air pipe to the inside of the blow pipe whose tip is connected to the tuyere of the blast furnace, supplying the hot air from the tuyere into the furnace via the inside of the blow pipe,
A second solid reducing material is introduced from the inner pipe of the second double pipe lance having a tip inserted into the blow pipe, and a flammable reducing gas is introduced from the outer pipe to the inside of the blow pipe. A blast furnace operating method that is simultaneously blown and supplied into the furnace from the tuyere,
A method for operating a blast furnace, characterized in that a flammable reducing gas injection index B defined by the following formula (2) is set to 300 to 100,000.
B = V ₂ × F ₂ (2)
here,
V ₂ : Corrected gas flow rate (m / s) of the flammable reducing gas at the tip of the second double pipe lance, calculated by the following equation (4)
F ₂ : Gas flow rate of flammable reducing gas per lance (Nm ³ / h)
And
_{_{V 2 = {(G 2/}} 3600) × (T 2 /273.15)×(P A / P B)} / S 2 ··· (4)
In
G ₂ : Gas flow rate of flammable reducing gas in standard state (Nm ³ / h)
T ₂ : temperature of the flammable reducing gas (K)
P _A : Atmospheric pressure (kPa)
P _B : Hot air blowing pressure (kPa)
S ₂ : Cross-sectional area of the flammable reducing gas in the second double-pipe lance (m ² )
It is.

10. The blast furnace operation according to 9, wherein the flammable reducing gas is one or more selected from city gas, natural gas, propane gas, hydrogen, converter gas, blast furnace gas, and coke oven gas. Method.

11. The blast furnace operating method according to 9 or 10, wherein the flammable reducing gas is blown in a range of 0.1 kg to 50 kg per 1 ton of pig iron.

12 The blast furnace operating method according to any one of 1 to 11, wherein the solid reducing material is pulverized coal.

13. The blast furnace operating method according to any one of 1 to 12, wherein the solid reducing material is blown in a range of 50 kg to 300 kg per 1 ton of pig iron.

According to the present invention, the flammability of the solid reducing material injected through the lance is improved without affecting the lance, and the blast furnace operation with a low coke ratio and a low reducing material ratio is stably performed. Can do.

It is a schematic diagram which shows the experimental apparatus used for the combustion experiment of 1st invention. It is a schematic diagram which shows the evaluation point of the dispersibility of pulverized coal. It is a schematic diagram which shows the experimental apparatus used for the combustion experiment of 2nd invention. It is a schematic diagram which shows the experimental apparatus used for the combustion experiment of 3rd invention.

Hereinafter, the present invention will be specifically described.
The present invention takes the following three modes for its implementation.
(1) The first and second double pipe lances are used, and the first solid pipe and the combustion-supporting gas are supplied from the first double pipe lance from the second double pipe lance. Is a method (hereinafter referred to as the first invention) in which a second solid reducing material and a flammable reducing gas are respectively injected.
(2) A method in which only the first double-pipe lance is used and the first solid reducing material and the combustion-supporting gas are blown from the double-pipe lance (hereinafter referred to as the second invention).
(3) A method in which only the second double pipe lance is used and the second solid reducing material and the flammable reducing gas are blown from the double pipe lance (hereinafter referred to as the third invention).

First, the first invention will be described.
A combustion experiment for confirming the effect of the first invention was performed using the combustion experiment apparatus shown in FIG. The figure shows the solid reducing material in a balanced manner using two double-pipe lances, each of which is connected to the tip of the blast furnace tuyere, and inside the blow pipe where hot air flows from the hot air pipe. The state which injects property gas, a solid reducing material, and a combustible reducing gas is shown, respectively.
In this combustion experiment, pulverized coal 2 was blown from the inner pipe of the first double pipe lance 1 as a first solid reducing material, and oxygen 3 was blown from the outer pipe as a supporting gas. On the other hand, pulverized coal 5 was blown from the inner pipe of the second double pipe lance 4 as a second solid reducing material, and city gas 6 was blown from the outer pipe as a flammable reducing gas. Furthermore, in this combustion experiment, in order to change the flow rate with the same flow rates of oxygen and city gas, various double pipe lances with different cross-sectional areas of the flow passage gaps were prepared and injected. In the figure, reference numeral 7 denotes a potential core, which indicates a region where the blown oxygen, the city gas, and the blown gas are not mixed. 8 is a blow pipe.

As experimental conditions, specifications of pulverized coal per lance are: fixed carbon (FC) 77.8 mass%, volatile matter (VM) 13.6 mass%, ash (Ash) 8.6 mass% The blowing condition was 31.0 kg / h (equivalent to 90 kg per 1 ton of pig iron). The oxygen blowing conditions were a gas temperature (T ₁ ) of 20 ° C., a flow rate (F ₁ ) of 4.5 to 20 Nm ³ / h, and 19 to 83 kg per ton of pig iron. On the other hand, the city gas blowing conditions were a gas temperature (T ₂ ) of 20 ° C., a flow rate (F ₂ ) of 0.49 to 5 Nm ³ / h, and 1 to 10 kg per 1 ton of pig iron. The blowing conditions are: blowing temperature 1200 ° C., blowing pressure (P _B ) 120 kPa, flow rate 350 Nm ³ / h, flow rate 150 m / s, oxygen enrichment +1.5 vol% (oxygen concentration 22.5 vol%, oxygen concentration in air 21 vol%) And 1.5 vol% enrichment). N ₂ gas was used as the carrier gas for the pulverized coal. The atmospheric pressure (P _A ) was 101.3 kPa.

The evaluation of the experimental results was based on the combustion temperature and dispersibility of pulverized coal in the case of a normal oxygen blowing index and a city gas blowing index (test symbol A). The oxygen injection index A and the city gas injection index B are values defined by the following expressions (1) and (2), respectively.
A = V ₁ × F ₁ (1)
B = V ₂ × F ₂ (2)
here,
V ₁ : Corrected gas flow velocity (m / s) of the combustion-supporting gas (oxygen) at the tip of the first double pipe lance, calculated by the following equation (3)
F ₁ : Gas flow rate of combustion-supporting gas (oxygen) per lance (Nm ³ / h)
V ₂ : Corrected gas flow velocity (m / s) of the flammable reducing gas (city gas) at the tip of the second double pipe lance, calculated by the following equation (4)
F ₂ : Gas flow rate of flammable reducing gas (city gas) per lance (Nm ³ / h)
Note that the F _1, F _2, the gas flow rate in the pipe connected to the lance was measured by the gas flow meter.

Further, each of the oxygen flow rate V ₁ and city gas flow velocity V ₂ at the lance tip, the following equation corrected by the oxygen or the gas temperature and the blowing pressure of the city gas (3), was calculated using (4).
_{_{V 1 = {(G 1/}} 3600) × (T 1 /273.15)×(P A / P B)} / S 1 ··· (3)
_{_{V 2 = {(G 2/}} 3600) × (T 2 /273.15)×(P A / P B)} / S 2 ··· (4)
here,
G ₁ : Gas flow rate of combustion-supporting gas (oxygen) in the standard state (Nm ³ / h)
G ₂ : Gas flow rate (Nm ³ / h) of flammable reducing gas (city gas) in the standard state
T ₁ : Temperature of supporting gas (oxygen) (K)
T ₂ : Temperature (K) of flammable reducing gas (city gas)
P _A : Atmospheric pressure (kPa)
P _B : Hot air blowing pressure (kPa)
S ₁ : Cross-sectional area (m ² ) of the combustion-supporting gas (oxygen) in the first double-pipe lance
S ₂ : Channel cross-sectional area (m ² ) of flammable reducing gas (city gas) in the second double pipe lance
T ₁ , T ₂ , and P _B are T ₁ and T ₂ in the pipe connected to the lance, P _B is the position in the blow pipe, T ₁ and T ₂ are thermocouple thermometers, and P _B is Measured with a pressure gauge.

Furthermore, the combustion temperature was measured using a two-color thermometer, and the dispersibility of pulverized coal was measured using a high-speed camera. In either case, measurement was performed at a position 50 mm from the tip of the double tube lance.

As described above, the oxygen injection index A and the city gas injection index B, the combustibility, and the dispersibility of the pulverized coal when the combustion experiment was performed with various oxygen and city gas injection conditions changed. The results of examining the relationship are shown in Tables 1 and 2.
The dispersibility of the pulverized coal was evaluated by the maximum spread angle θ of the pulverized coal at a position 50 mm from the tip of the double pipe lance as shown in the schematic diagram of FIG. It can be said that the greater the θ, the better the dispersibility of the pulverized coal. In addition, in the comprehensive evaluation, a case where both the combustion temperature and dispersibility are approximately the same as the case of the normal city gas injection index of 110000 (test symbol A) is indicated by Δ, and a case where it is improved is indicated by ○.
Tables 1 and 2 also show the results of examining the relationship between the blowing index, the lance surface temperature, and the presence or absence of lance melting in the above combustion experiment. The surface temperature at the tip of the lance was measured with a thermoviewer.

As shown in Tables 1 and 2, when the oxygen injection index A and the city gas injection index B calculated using the formulas (1) and (2) are 100000 or less, the combustion temperature and the pulverized coal Both dispersibility is improved.

The reason for this is presumed that, as shown in FIG. 1, the length of the potential core 7, which is a region where oxygen, city gas, and blown gas do not mix, is shortened when the oxygen or city gas blowing index decreases. . When the length of the potential core 7 is shortened, the dispersibility of the pulverized coal particles is improved, the mixing property of the pulverized coal particles and the blowing gas is improved, the temperature rise of the pulverized coal particles is improved, and finally the combustibility is improved. It is thought that it is done.
In particular, in the first invention in which oxygen and city gas are used in combination, a lance that blows pulverized coal and oxygen and a lance that blows pulverized coal and city gas are close to each other. The city gas reacts and the city gas burns, causing rapid heating and ignition of the pulverized coal, which further improves the combustibility of both lances. Further, by reducing the amount of pulverized coal by half, the dispersibility of the pulverized coal is also improved, so that the combustibility is further improved.

On the other hand, as shown in Tables 1 and 2, when the oxygen blowing index A and the city gas blowing index B exceed 100,000 (test symbol B), the dispersibility of the pulverized coal is not improved. When the oxygen blowing index A is less than 100 or the city gas blowing index B is less than 300 (test symbols K and L), the surface temperature of the lance rises and the heat resistance of the stainless steel material used for the lance is increased. It was found that the temperature was higher than 1150 ° C. and lance erosion occurred.
Furthermore, as shown by the test symbol M, when the city gas was injected properly but oxygen was not injected properly, or as shown by the test symbol N, the oxygen was injected properly but the city was None of the satisfactory results were obtained with respect to the dispersibility of the pulverized coal when the gas injection was inadequate.

Therefore, in order to improve flammability by blowing pulverized coal and city gas stably without causing deformation of the lance or melting damage, the oxygen blowing index A is set to 100 or more and 100000 or less, and city gas blowing It has been determined that the inclusion index B needs to be 300 or more and 100,000 or less.

In the first invention (the same applies to the second and third inventions described later), pulverized coal is advantageously adapted as the first and second solid reducing materials. In addition, solid reducing materials such as waste plastics, waste solid fuel, organic resources, and waste materials can be mixed and used in pulverized coal. Here, the mixing amount of the solid reducing material other than pulverized coal is preferably 20 mass% or less.
The amount of the solid reducing material blown is preferably 50 to 300 kg per 1 ton of pig iron.

Further, in the first invention (the same applies to the second invention described later), oxygen is preferable as the supporting gas, but oxygen-enriched air having oxygen of 22 vol% or more is also advantageously adapted. To do. Thus, if the oxygen concentration in the supporting gas exceeds the oxygen concentration in the air, the contact property between the pulverized coal and oxygen is improved, and the combustibility is improved.
In addition, the amount of the gas to be supported is preferably 9 to 370 kg per ton of pig iron.

Furthermore, in the first invention (the same applies to the third invention described later), the flammable reducing gas includes natural gas, propane gas, hydrogen, converter gas, blast furnace gas, coke oven as well as the above-mentioned city gas. Gas and the like are advantageously suitable. The amount of the flammable reducing gas blown is preferably 0.1 to 50 kg per ton of pig iron. More preferably, it is 10 kg / t-pig iron or less.

In the first invention (the same applies to the second and third inventions to be described later), as the blown gas (also referred to as hot air) blown into the blast furnace through the blow pipe, a gas passing through the hot stove is usually used. Is done. Accordingly, the blowing temperature and blowing pressure indicate the gas temperature and gas pressure of the gas passing through the hot stove.

Next, the second invention will be described.
As in the case of the first invention, a combustion experiment for confirming the effect of the second invention was performed using the combustion experiment apparatus shown in FIG. This figure shows a case where only the first double pipe lance 1 is used in the combustion experiment of the first invention shown in FIG. 1, and the fine powder is used as the first solid reducing material from the inner pipe of the double pipe lance 1. Oxygen 3 was blown in as charcoal 2 and as a supporting gas from the outer tube. In this combustion experiment, various double-pipe lances with different cross-sectional areas of the flow passage gap were prepared and injected in order to change the flow rate with the same oxygen flow rate.

As experimental conditions, the specifications of pulverized coal are 77.8 mass% of fixed carbon (FC), 13.6 mass% of volatile matter (VM), 8.6 mass% of ash (Ash), and blowing conditions. Was 62.0 kg / h (equivalent to 180 kg per ton of pig iron). The oxygen blowing conditions were a gas temperature (T ₁ ) of 20 ° C., a flow rate (F ₁ ) of 4.5 to 20 Nm ³ / h, and 19 to 83 kg per ton of pig iron. The blowing conditions are: blowing temperature 1200 ° C., blowing pressure (P _B ) 120 kPa, flow rate 350 Nm ³ / h, flow rate 150 m / s, oxygen enrichment +1.5 vol% (oxygen concentration 22.5 vol%, oxygen concentration in air 21 vol%) And 1.5 vol% enrichment). N ₂ gas was used as the carrier gas for the pulverized coal. The atmospheric pressure (P _A ) was 101.3 kPa.

Evaluation of the experimental results was based on the combustion temperature and dispersibility of pulverized coal in the case of a normal oxygen blowing index (No. 1). Here, the oxygen injection index A is a value defined by the following equation (1).
A = V ₁ × F ₁ (1)
here,
V ₁ : Corrected gas flow velocity (m / s) of the combustion-supporting gas (oxygen) at the tip of the first double pipe lance, calculated by the following equation (3)
F ₁ : Gas flow rate of combustion-supporting gas (oxygen) per lance (Nm ³ / h)

The oxygen flow velocity V ₁ at the tip of the lance was calculated using the following equation (3) corrected by the oxygen gas temperature and the blowing pressure.
_{_{V 1 = {(G 1/}} 3600) × (T 1 /273.15)×(P A / P B)} / S 1 ··· (3)
In
G ₁ : Gas flow rate of combustion-supporting gas (oxygen) in the standard state (Nm ³ / h)
T ₁ : Temperature of supporting gas (oxygen) (K)
P _A : Atmospheric pressure (kPa)
P _B : Hot air blowing pressure (kPa)
S ₁ : Cross-sectional area (m ² ) of the combustion-supporting gas (oxygen) in the first double-pipe lance

The combustion temperature was measured at a position 50 mm from the tip of the double tube lance using a two-color thermometer. Further, the dispersibility of the pulverized coal was evaluated by the maximum spread angle θ of the pulverized coal at a position 50 mm from the tip of the double pipe lance using a high-speed camera.

Table 3 shows the results of examining the relationship between the oxygen injection index A, the combustibility, and the dispersibility of the pulverized coal when the combustion experiment was performed with various changes in the oxygen injection conditions as described above. Shown in
The overall evaluation is indicated by Δ when the combustion temperature and dispersibility are both about the same as the case of 110000 (No. 1), which is a normal oxygen blowing index, and by ○ when it is improved.
Table 3 also shows the results of examining the relationship between the oxygen blowing index A, the lance surface temperature, and the presence / absence of lance melting in the above combustion experiment. The surface temperature at the tip of the lance was measured with a thermoviewer.

As shown in the table, when the oxygen injection index A calculated using the formula (1) is 100,000 or less, it is clear that both the combustion temperature and the dispersibility of the pulverized coal are improved.

The reason for this is presumed that, as shown in FIG. 3, when the oxygen blowing index decreases, the length of the potential core 7 which is a region where oxygen and the blown gas are not mixed decreases. When the length of the potential core 7 is shortened, the dispersibility of the pulverized coal particles is improved, the mixing property of the pulverized coal particles and the blowing gas is improved, the temperature rise of the pulverized coal particles is improved, and finally the combustibility is improved. It is thought that it is done.
In the second invention using only oxygen, since oxygen is cheaper than city gas, operation at a lower cost is achieved.

On the other hand, as shown in Table 3, when the oxygen blowing index A exceeded 100,000 (No. 2), the dispersibility of the pulverized coal was inferior. Further, when the oxygen blowing index A is less than 100 (Nos. 11 and 12), the surface temperature of the lance rises and becomes higher than the heat resistant temperature of 1150 ° C. of the stainless steel material used for the lance, and the lance is melted. I understood.

Therefore, in order to improve flammability by blowing pulverized coal and oxygen stably without causing lance deformation or erosion, the oxygen blowing index A needs to be 100 or more and 100,000 or less. confirmed.

Next, the third invention will be described.
As in the case of the first invention, a combustion experiment for confirming the effect of the third invention was performed using the combustion experiment apparatus shown in FIG. This figure shows a case where only the second double pipe lance 4 is used in the combustion experiment of the first invention shown in FIG. 1, and the fine powder is used as the second solid reducing material from the inner pipe of the double pipe lance 4. Charcoal 5 and city gas 6 were blown from the outer pipe as flammable reducing gas. Moreover, in this combustion experiment, since the flow rate of the city gas was the same and the flow rate was changed, various double pipe lances with different cross-sectional areas of the flow passage gaps were prepared and injected.

As experimental conditions, the specifications of pulverized coal are 77.8 mass% of fixed carbon (FC), 13.6 mass% of volatile matter (VM), 8.6 mass% of ash (Ash), and blowing conditions. Was 62.0 kg / h (equivalent to 180 kg per ton of pig iron). The city gas was injected under the conditions of a gas temperature (T ₂ ) of 20 ° C., a flow rate (F ₂ ) of 0.49 to 5 Nm ³ / h, and 10 kg per ton of pig iron. The blowing conditions are: blowing temperature 1200 ° C., blowing pressure (P _B ) 120 kPa, flow rate 350 Nm ³ / h, flow rate 150 m / s, oxygen enrichment +5.5 vol% (oxygen concentration 26.5 vol%, air oxygen concentration 21 vol%) On the other hand, it was 5.5 vol% enrichment). N ₂ gas was used as the carrier gas for the pulverized coal. The atmospheric pressure (P _A ) was 101.3 kPa.

The evaluation of the experimental results was based on the combustion temperature and dispersibility of pulverized coal in the case of a normal city gas injection index (No. 21). Here, the city gas injection index B is a value defined by the following equation (2).
B = V ₂ × F ₂ (2)
here,
V ₂ : Corrected gas flow velocity (m / s) of the flammable reducing gas (city gas) at the tip of the second double pipe lance, calculated by the following equation (4)
F ₂ : Gas flow rate of flammable reducing gas (city gas) per lance (Nm ³ / h)

Further, city gas flow velocity V ₂ at the lance tip was calculated using the following equation corrected by the gas temperature and the blowing pressure of the city gas (4).
_{_{V 2 = {(G 2/}} 3600) × (T 2 /273.15)×(P A / P B)} / S 2 ··· (4)
here,
G ₂ : Gas flow rate (Nm ³ / h) of flammable reducing gas (city gas) in the standard state
T ₂ : Temperature (K) of flammable reducing gas (city gas)
P _A : Atmospheric pressure (kPa)
P _B : Hot air blowing pressure (kPa)
S ₂ : Channel cross-sectional area (m ² ) of flammable reducing gas (city gas) in the second double pipe lance

As described above, the results of examining the relationship between the city gas injection index B and the combustibility and dispersibility of the pulverized coal when the combustion experiment was performed by variously changing the gas gas injection conditions, Table 4 shows.
In addition, in the comprehensive evaluation, the case where both the combustion temperature and dispersibility are about the same as the case of 110000 which is a normal city gas injection index (No. 21) is indicated by Δ, and the case where it is improved is indicated by ○.
Table 4 also shows the results of examining the relationship between the city gas injection index B, the lance surface temperature, and the presence or absence of lance melting in the above combustion experiment. The surface temperature at the tip of the lance was measured with a thermoviewer.

As shown in the table, it was revealed that both the combustion temperature and the dispersibility of pulverized coal were improved when the city gas injection index B calculated using the formula (2) was 100,000 or less. .

The reason for this is presumed that, as shown in FIG. 4, when the city gas injection index decreases, the length of the potential core 7, which is a region where the city gas and the blown gas are not mixed, is shortened. When the length of the potential core 7 is shortened, the dispersibility of the pulverized coal particles is improved, the mixing property of the pulverized coal particles and the blowing gas is improved, the temperature rise of the pulverized coal particles is improved, and finally the combustibility is improved. It is thought that it is done.
In the third invention using only city gas, since the city gas is a flammable gas and is superior to oxygen in terms of ignitability, the coke ratio is further reduced than in the second invention using only oxygen. Can do.

On the other hand, as shown in Table 4, when the city gas injection index B exceeded 100,000 (No. 22), the dispersibility of the pulverized coal was inferior. Further, when the city gas injection index B is less than 300 (No. 31, 32), the surface temperature of the lance rises and becomes higher than the heat resistant temperature of 1150 ° C. of the stainless steel material used for the lance, and the lance is melted. I understood that.

Therefore, in order to improve flammability by injecting pulverized coal and city gas stably without causing deformation or melting of the lance, it is necessary to set the city gas injection index B to 300 or more and 100000 or less. Was found.

Example 1
In blast furnace having an inner volume of 5000 m ³ with tuyeres 38 present, the target pig iron production 11500t / day, pulverized coal ratio 150 kg / t-pig iron, inclusive oxygen flow from an oxygen blowing lance weight 74 kg / t-pig iron, city gas blown The experiment was conducted under the conditions of a city gas blowing rate of 10 kg / t-pig iron, oxygen, and a city gas temperature of 20 ° C., a blowing temperature of 1200 ° C., a blowing pressure of 520 kPa, and a blowing oxygen enrichment + 1.5 vol%. Then, using two double pipe lances, lances having different oxygen blowing index A and city gas blowing index B under the condition that pulverized coal is blown from the inner pipe and oxygen and city gas are blown from the outer pipe, respectively. In each case, the operation was carried out for 3 days, and the change in the average coke ratio (kg / t-pig iron) was recorded to investigate the operation effect.
Table 5 shows the results of examining the relationship between the oxygen injection index A and the city gas injection index B and the coke ratio in the above blast furnace operation. In calculating the oxygen blowing index A and the city gas blowing index B, the oxygen flow rate and the city gas flow rate at the tip of the lance were calculated by the equations (3) and (4).

As shown in the table, the coke ratio was 370 kg / t-pig iron when either or both of the oxygen injection index A and the city gas injection index B were 110,000 or 105000 lances. In the case where both the index A and the index B use a lance of 100,000, 368 kg / t-pig iron, and when the index A and the index B use a lance of 10,000,100,000, respectively, 367 kg / t- pig iron When the same index A and index B use lances of 100,000 and 10,000, respectively, 366 kg / t-pig iron, when both the index A and index B use 10,000 lances, 365 kg / t- pig iron 363 kg / t-pig iron when A and B have 100 and 300 lances, respectively In was reduced.

From the above results, the length of the potential core at the tip of the lance is reduced by adjusting the oxygen injection index A and the city gas injection index B to a predetermined range according to the first invention, and the pulverized coal particles and the blast It has been found that the miscibility with oxygen in the gas, and hence the combustibility, is improved, and as a result, a reduction in the coke ratio and reducing material ratio is achieved.
Moreover, as a result of taking out each lance after the operation when the lances having oxygen injection index A and city gas injection index B of 100,300 were used and examining the tip of the lance, no deformation or erosion was observed. .
Therefore, according to the first invention, when a lance having an oxygen injection index A of 100 to 100,000 and a city gas injection index B of 300 to 100,000 is used, the blast furnace operation with the above-mentioned low coke ratio and low reducing material ratio is performed. It was confirmed that it could be implemented stably without adversely affecting the lance.

(Example 2)
In a blast furnace with an inner volume of 5000 m ³ with 38 tuyere, target pig iron production of 11500 t / day, pulverized coal ratio of 150 kg / t-pig iron, oxygen temperature of 20 ° C. when oxygen is blown from the lance, oxygen blow quantity of 74 kg The experiment was conducted under the conditions of / t-pig iron, air blowing temperature 1200 ° C., air blowing pressure 520 kPa, air blowing oxygen enrichment + 1.5 vol%. Then, under the condition that pulverized coal is blown from the inner pipe of the double pipe lance and oxygen is blown from the outer pipe, the operation is carried out for 3 days using different lances with different oxygen blowing indexes A, and the average coke ratio (kg / t -Recorded changes in pig iron) and investigated operational effects.
Table 6 shows the results of examining the relationship between the oxygen blowing index A and the coke ratio in the above blast furnace operation. In calculating the oxygen blowing index A, the oxygen flow rate at the tip of the lance was calculated by equation (3).

As shown in the table, when using a lance with an oxygen injection index A of 110000 or 105000, the coke ratio was 375 kg / t-pig iron, whereas when using a lance with an index A of 100,000 In the case of using a lance with 374 kg / t-pig iron and index A of 10,000, the coke ratio is reduced to 373 kg / t-pig iron and when using a lance with index A of 100, the coke ratio is reduced to 372 kg / t-pig iron. did.

From the above results, the length of the potential core at the tip of the lance is reduced by adjusting the oxygen injection index A to a predetermined range according to the second invention, and mixing of the pulverized coal particles and oxygen in the blowing gas As a result, it has been found that the coke ratio and the reducing material ratio are reduced.
Further, as a result of examining the tip of the lance after taking out the lance after the operation in the case where the lance having the oxygen blowing index A of 100 was used, no deformation or damage was found.
Therefore, according to the second invention, when a lance having an oxygen injection index A adjusted to 100 to 100000 is used, the above-mentioned blast furnace operation with a low coke ratio and a low reducing material ratio can be performed without adversely affecting the lance. It was confirmed that it could be carried out stably.

(Example 3)
In a blast furnace with an inner volume of 5000 m ³ with 38 tuyere, target pig iron production of 11500 t / day, pulverized coal ratio of 150 kg / t-pig iron, city gas injection from the lance of 10 kg / t-pig iron, city gas temperature of 20 The experiment was performed under the conditions of a blast temperature of 1200 ° C., a blast pressure of 520 kPa, and a blast oxygen enrichment of 5.5 vol%. Then, under conditions where pulverized coal is blown from the inner pipe of the double pipe lance and city gas is blown from the outer pipe, operation is carried out for 3 days using different lances with different city gas blowing indices B, and the average coke ratio (kg / T-pig iron) was recorded to investigate the operational effect. The city gas flow velocity at the tip of the lance was calculated by equation (1).
Table 7 shows the results of examining the relationship between the city gas injection index B and the coke ratio in the above blast furnace operation. In calculating the city gas injection index B, the city gas flow velocity at the tip of the lance was calculated by equation (4).

As shown in the table, when the lances with city gas injection index B of 110,000 and 105000 were used, the coke ratio was 373 kg / t-pig iron, whereas the lance with index B of 100,000 was used. In the case of using a lance with 372 kg / t-pig iron and index B of 10,000, the coke ratio is 371 kg / t-pig iron, and when using a lance with index B of 300, the coke ratio is up to 370 kg / t-pig iron. Reduced.

From the above results, according to the third invention, by adjusting the city gas injection index B to a predetermined range, the length of the potential core at the tip of the lance is reduced, and the pulverized coal particles and the oxygen in the blowing gas are reduced. It has been found that the mixability and thus the flammability is improved, so that a reduction in the coke ratio and reducing material ratio is achieved.
Moreover, as a result of taking out the lance after the operation when the lance having the city gas injection index B of 300 was used and examining the tip of the lance, no deformation or erosion was observed.
Therefore, in accordance with the third invention, when a lance having a city gas injection index B adjusted to 300 to 100,000 is used, the above-mentioned blast furnace operation with a low coke ratio and a low reducing material ratio does not adversely affect the lance. It was confirmed that it can be carried out stably.

DESCRIPTION OF SYMBOLS 1 1st double pipe lance 2 1st solid reducing material (pulverized coal)
3 gas (oxygen)
4 Second double pipe lance 5 Second solid reducing material (pulverized coal)
6 Flammable reducing gas (city gas)
7 Potential core 8 Blow pipe

Claims

Supplying hot air from the hot air pipe to the inside of the blow pipe whose tip is connected to the tuyere of the blast furnace, supplying the hot air from the tuyere into the furnace via the inside of the blow pipe,
A first solid reducing material is blown from the inner pipe of the first double pipe lance whose tip is inserted into the blow pipe, and a combustion-supporting gas is blown into the blow pipe simultaneously from the outer pipe. Then, supply from the tuyere into the furnace,
A second solid reducing material is introduced from the inner pipe of the second double pipe lance having a tip inserted into the blow pipe, and a flammable reducing gas is introduced from the outer pipe to the inside of the blow pipe. A blast furnace operating method that is simultaneously blown and supplied into the furnace from the tuyere,
The combustion support gas injection index A defined by the following formula (1) is set to 100 or more and 100000 or less, and the combustion index of the flammable reducing gas defined by the following formula (2) A method of operating a blast furnace, characterized in that B is 300 to 100000.
A = V 1 × F 1 (1)
B = V 2 × F 2 (2)
here,
V 1 : Corrected gas flow velocity (m / s) of the combustion-supporting gas at the tip of the first double pipe lance, calculated by the following equation (3)
F 1 : Gas flow rate of combustion-supporting gas per lance (Nm 3 / h)
V 2 : Corrected gas flow rate (m / s) of the flammable reducing gas at the tip of the second double pipe lance, calculated by the following equation (4)
F 2 : Gas flow rate of flammable reducing gas per lance (Nm 3 / h)
And
V 1 = {(G 1/ 3600) × (T 1 /273.15)×(P A / P B)} / S 1 ··· (3)
V 2 = {(G 2/ 3600) × (T 2 /273.15)×(P A / P B)} / S 2 ··· (4)
In
G 1 : Gas flow rate of the combustion-supporting gas in the standard state (Nm 3 / h)
G 2 : Gas flow rate of flammable reducing gas in standard state (Nm 3 / h)
T 1 : Temperature of supporting gas (K)
T 2 : temperature of the flammable reducing gas (K)
P A : Atmospheric pressure (kPa)
P B : Hot air blowing pressure (kPa)
S 1 : Cross-sectional area of the combustion-supporting gas in the first double-pipe lance (m 2 )
S 2 : Cross-sectional area of the flammable reducing gas in the second double-pipe lance (m 2 )
It is.
The method for operating a blast furnace according to claim 1, wherein the combustion-supporting gas is oxygen.
The blast furnace operating method according to claim 1 or 2, wherein the combustion-supporting gas is injected in a range of 9 kg to 370 kg per ton of pig iron.
The flammable reducing gas is one or more selected from city gas, natural gas, propane gas, hydrogen, converter gas, blast furnace gas, and coke oven gas. A blast furnace operating method according to claim 1.
The blast furnace operating method according to any one of claims 1 to 4, wherein the flammable reducing gas is injected in a range of 0.1 kg to 50 kg per ton of pig iron.
Supplying hot air from the hot air pipe to the inside of the blow pipe whose tip is connected to the tuyere of the blast furnace, supplying the hot air from the tuyere into the furnace via the inside of the blow pipe,
A first solid reducing material is blown from the inner pipe of the first double pipe lance whose tip is inserted into the blow pipe, and a combustion-supporting gas is blown into the blow pipe simultaneously from the outer pipe. In the blast furnace operating method of supplying into the furnace from the tuyere,
A method for operating a blast furnace, characterized in that an injection index A of the combustion-supporting gas defined by the following formula (1) is 100 or more and 100000 or less.
A = V 1 × F 1 (1)
here,
V 1 : Corrected gas flow velocity (m / s) of the combustion-supporting gas at the tip of the first double pipe lance, calculated by the following equation (3)
F 1 : Gas flow rate of combustion-supporting gas per lance (Nm 3 / h)
And
V 1 = {(G 1/ 3600) × (T 1 /273.15)×(P A / P B)} / S 1 ··· (3)
In
G 1 : Gas flow rate of the combustion-supporting gas in the standard state (Nm 3 / h)
T 1 : Temperature of supporting gas (K)
P A : Atmospheric pressure (kPa)
P B : Hot air blowing pressure (kPa)
S 1 : Cross-sectional area of the combustion-supporting gas in the first double-pipe lance (m 2 )
It is.
The blast furnace operating method according to claim 6, wherein the combustion-supporting gas is oxygen.
The blast furnace operating method according to claim 6 or 7, wherein the combustion-supporting gas is injected in a range of 9 kg to 370 kg per ton of pig iron.
Supplying hot air from the hot air pipe to the inside of the blow pipe whose tip is connected to the tuyere of the blast furnace, supplying the hot air from the tuyere into the furnace via the inside of the blow pipe,
A second solid reducing material is introduced from the inner pipe of the second double pipe lance having a tip inserted into the blow pipe, and a flammable reducing gas is introduced from the outer pipe to the inside of the blow pipe. A blast furnace operating method that is simultaneously blown and supplied into the furnace from the tuyere,
A method for operating a blast furnace, characterized in that a flammable reducing gas injection index B defined by the following formula (2) is set to 300 to 100,000.
B = V 2 × F 2 (2)
here,
V 2 : Corrected gas flow rate (m / s) of the flammable reducing gas at the tip of the second double pipe lance, calculated by the following equation (4)
F 2 : Gas flow rate of flammable reducing gas per lance (Nm 3 / h)
And
V 2 = {(G 2/ 3600) × (T 2 /273.15)×(P A / P B)} / S 2 ··· (4)
In
G 2 : Gas flow rate of flammable reducing gas in standard state (Nm 3 / h)
T 2 : temperature of the flammable reducing gas (K)
P A : Atmospheric pressure (kPa)
P B : Hot air blowing pressure (kPa)
S 2 : Cross-sectional area of the flammable reducing gas in the second double-pipe lance (m 2 )
It is.
The blast furnace according to claim 9, wherein the flammable reducing gas is one or more selected from the group consisting of city gas, natural gas, propane gas, hydrogen, converter gas, blast furnace gas, and coke oven gas. Operation method.
The blast furnace operating method according to claim 9 or 10, wherein the flammable reducing gas is blown in a range of 0.1 kg to 50 kg per ton of pig iron.
The blast furnace operating method according to any one of claims 1 to 11, wherein the solid reducing material is pulverized coal.
The blast furnace operating method according to any one of claims 1 to 12, wherein the solid reducing material is blown in a range of 50 kg to 300 kg per ton of pig iron.