Method for operating blast furnace and method for producing molten pig iron

Patent metadata

Field	Value
Publication number	US-9816151-B2
Application number	US-201314439622-A
Country	US
Kind code	B2
Filing date	Dec 4, 2013
Priority date	Dec 7, 2012
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

Provided is a blast-furnace operating method including: a first step of adjusting a charging rate of coke while monitoring a furnace-top temperature T top ; a second step of adjusting an injection rate of pulverized coal while monitoring an in-furnace superficial gas velocity u and the furnace-top temperature T top ; a third step of adjusting an oxygen-enrichment ratio of oxygen-enriched air while monitoring a tuyere combustion temperature T f and the furnace-top temperature T top ; and a fourth step of determining whether an injection rate of the oxygen-enriched air needs to be adjusted, based on a value of the in-furnace superficial gas velocity u.

First claim

The invention claimed is:

1. A blast-furnace operating method in which iron-oxide raw material is reduced to obtain molten pig iron by charging the iron-oxide raw material, coke, and partially reduced iron from the furnace top of a blast furnace, and also injecting pulverized coal and oxygen-enriched air from a tuyere of the blast furnace, the blast-furnace operating method comprising:
a first step of adjusting a charging rate of the coke while monitoring a furnace-top temperature T top ;
a second step of adjusting an injection rate of the pulverized coal while monitoring an in-furnace superficial gas velocity u and the furnace-top temperature T top ;
a third step of adjusting an oxygen-enrichment ratio of the oxygen-enriched air while monitoring a combustion temperature T f at the tuyere and the furnace-top temperature T top ; and
a fourth step of determining whether an injection rate of the oxygen-enriched air needs to be adjusted, based on a value of the in-furnace superficial gas velocity u.

2. The blast-furnace operating method according to claim 1 , wherein
when a charging rate of the partially reduced iron is increased, at the first step, the charging rate of the coke is decreased within a range where the furnace-top temperature T top satisfies the following expression (1):
T top >T topmin   (1)

wherein T topmin is a given temperature that is set within a range equal to or lower than 120° C.;
at the second step, the injection rate of the pulverized coal is increased within ranges where the in-furnace superficial gas velocity u and the furnace-top temperature T top respectively satisfy the following expressions (2) and (3):
u≦u max   (2)

T top ≦T topmax   (3)

wherein u max is a given velocity that is set within a range from 100 to 150 m/min, and T topmax is a given temperature that is set within a range equal to or higher than 180° C.;
at the third step, the oxygen-enrichment ratio is increased within a range where the furnace-top temperature T top and the combustion temperature T f respectively satisfy the above expression (1) and the following expression (4):
T f ≦T fmax   (4)

wherein T fmax is a given temperature that is set within a range equal to or higher than 2300° C.; and
at the fourth step, if the in-furnace superficial gas velocity u does not satisfy the above expression (2), the injection rate of the oxygen-enriched air is decreased so that the in-furnace superficial gas velocity u satisfies the above expression (2).

3. The blast-furnace operating method according to claim 1 , wherein after the fourth step, the second step, the third step, and the fourth step are repeatedly performed until the in-furnace superficial gas velocity u satisfies the following expression (5):
u=u max   (5), and/or

until the furnace-top temperature T top satisfies the following expression (6):
T top =T topmin   (6)

wherein u max is a given velocity that is set within a range from 100 to 150 m/min, and wherein T topmin is a given temperature that is set within a range equal to or lower than 120° C.

4. The blast-furnace operating method according to claim 1 , wherein after the fourth step, if the in-furnace superficial gas velocity u satisfies the following expression (7):
u<u max   (7),

the injection rate of the oxygen-enriched air is increased, and then the first step, the second step, the third step, and the fourth step are repeatedly performed, wherein u max is a given velocity that is set within a range from 100 to 150 m/min.

5. The blast-furnace operating method according to claim 1 , wherein after the fourth step, if the furnace-top temperature T top satisfies the following expression (8):
T top >T topmin   (8),

the first step, the second step, the third step, and the fourth step are repeatedly performed, wherein T topmin is a given temperature that is set within a range equal to or lower than 120° C.

6. The blast-furnace operating method according to claim 1 , wherein at the third step, the oxygen-enrichment ratio is adjusted within a range exceeding 8% and equal to or lower than 16%.

7. The blast-furnace operating method according to claim 1 , wherein the injection rate of the pulverized coal exceeds 130 kilograms per ton of molten pig iron.

8. The blast-furnace operating method according to claim 1 , wherein a charging rate of the partially reduced iron is 100 to 600 kilograms per ton of molten pig iron.

9. The blast-furnace operating method according to claim 1 , wherein a carbon content of the partially reduced iron is 2.3 to 5.9% by mass.

10. The blast-furnace operating method according to claim 1 , wherein a percentage of partially reduced iron having a particle diameter smaller than five millimeters in a whole of the partially reduced iron charged into the blast furnace is equal to or lower than 10% by mass.

11. The blast-furnace operating method according to claim 1 , wherein a crushing strength of the partially reduced iron charged into the blast furnace is equal to or higher than 30 kg/cm 2 .

12. A molten-pig-iron production method comprising producing molten pig iron by the blast-furnace operating method according to claim 1 .

13. The blast-furnace operating method according to claim 1 , wherein when an oxygen-enrichment ratio of the oxygen-enriched air is defined as x (%) and an injection rate of the pulverized coal per ton of molten pig iron is defined as y (kg/t), x and y satisfy the following expressions (9) and (10):
25 x− 175 <y< 31 x+ 31  (9)

y> 130  (10),

wherein a charging amount of the partially reduced iron is 100 to 600 kilograms per ton of molten pig iron, and
wherein the oxygen-enrichment ratio is adjusted within a range exceeding 8% and equal to or lower than 16%.

14. The blast-furnace operating method according to claim 13 , wherein a carbon content of the partially reduced iron is 2.3 to 5.9% by mass.

15. The blast-furnace operating method according to claim 13 , wherein a percentage of partially reduced iron having a particle diameter smaller than five millimeters in a whole of the partially reduced iron charged into the blast furnace is equal to or lower than 10% by mass.

16. The blast-furnace operating method according to claim 13 , wherein a crushing strength of the partially reduced iron charged into the blast furnace is equal to or higher than 30 kg/cm 2 .

17. A molten-pig-iron production method comprising producing the molten pig iron by the blast-furnace operating method according to claim 13 .

Assignees

• Nippon Steel & Sumikin Eng Co

Inventors

• Ichikawa Hiroshi
• OOSAWA Yasuyuki
• Hayashi Takafumi
• Tomisaki Shin

Classifications

• C21B5/008

  Composition or distribution of the charge · CPC title

• C21B5/00 Primary

  Making pig-iron in the blast furnace · CPC title

• C21B2300/04

  Modeling of the process, e.g. for control purposes; CII · CPC title

• C21B13/14

  Multi-stage processes {processes carried out in different vessels or furnaces} · CPC title

• C21B5/003

  Injection of pulverulent coal · CPC title