Method for operating converter

Patent metadata

Field	Value
Publication number	US-11124849-B2
Application number	US-201816611674-A
Country	US
Kind code	B2
Filing date	May 7, 2018
Priority date	May 8, 2017
Publication date	Sep 21, 2021
Grant date	Sep 21, 2021

Abstract

When the decarburization refining of molten iron is performed by top-blowing oxygen gas from the top blowing lance, the oscillation of molten iron, a bubble burst, and spitting due to the bubble burst are suppressed. A refining method for a converter includes decarburizing molten iron in the converter with a top blowing lance having Laval nozzles disposed at the lower end thereof by blowing oxygen gas on the surface of the molten iron in the converter through the Laval nozzles, in which one or both of an oxygen feeding rate from the top blowing lance and lance height LH are adjusted in such a manner that an oxygen accumulation index S(F) is 40 or less.

First claim

The invention claimed is:

1. A method for operating a converter, comprising:
a refining process including decarburizing molten iron in a converter with a top blowing lance having one or more Laval nozzles disposed at a lower end thereof by blowing oxygen gas on a surface of the molten iron in the converter through the one or more Laval nozzles,
wherein:
an oxygen gas flow rate F per unit hot spot area (Nm 3 /(m 2 ×s)) is determined by Formula (1) described below,
an oxygen accumulation index S(F) in the converter is determined from the oxygen gas flow rate F and Formula (2) described below, and
one or both of an oxygen feeding rate Q g from the top blowing lance and lance height LH are adjusted such that the oxygen accumulation index S(F) satisfies Formula (3) described below,

F
=

(

Q
g

n

)

1.2

π
6

×
r
×

[

(

r
2

+

4
⁢
L

)

3
2

-

r
3

]

×

(

4.8586
⁢

⁢

P
0
0.112

×

d
c

-
0.44

×

v
gc

1630

)

0.2

(
1
)

⁢

S
⁡

(
F
)

=

α
⁢

⁢

Σ
⁡

(

1

F
0

-

1
F

)

⁢
Δ
⁢

⁢
t

(
2
)

⁢

S
⁡

(
F
)

≤
40

(
3
)

where in Formula (1),
n is a number of the one or more Laval nozzles disposed at the lower end of the top blowing lance,
d c is a throat diameter (mm) of each of the one or more Laval nozzles,
Q g is the oxygen feeding rate (Nm 3 /s) from the top blowing lance,
P 0 is a supply pressure (Pa) of the oxygen gas to the one or more Laval nozzles,
v gc is an oxygen gas flow velocity calculated from the lance height LH (m) at a collision surface of the surface of the molten iron and is the oxygen gas flow velocity (m/s) along a central axis of each of the one or more Laval nozzles,
r is a radius (mm) of a cavity formed by colliding the oxygen gas with the surface of the molten iron, and
L is a depth (mm) of the cavity, and
where in Formula (2),
α is a constant ((m 2 ×s)/Nm 3 ),
F 0 is a constant (Nm 3 /(m 2 ×s)), and
Δt is a data collection time interval (s).

2. The method for operating a converter according to claim 1 , wherein:
an actu

Assignees

• Jfe Steel Corp

Inventors

• Amano Shota
• Takahashi Yukio
• Kikuchi Naoki
• Miki Yuji

Classifications

• C21C5/32 Primary

  Blowing from above (C21C5/35 takes precedence) · CPC title

• C21C5/5217

  equipped with burners or devices for injecting gas, i.e. oxygen, or pulverulent materials into the furnace · CPC title

• C21C5/52

  Manufacture of steel in electric furnaces {(C21C5/005 takes precedence)} · CPC title

• C21C5/4606

  Lances or injectors · CPC title