Molten iron dephosphorization method

Patent metadata

Field	Value
Publication number	US-2022259686-A1
Application number	US-202017626083-A
Country	US
Kind code	A1
Filing date	Jul 2, 2020
Priority date	Jul 22, 2019
Publication date	Aug 18, 2022
Grant date	—

Abstract

A dephosphorization method using a top and bottom blown converter. This method uses a converter charged with molten iron and slag, to blow an oxygen-containing gas from a top-blowing lance, supply the gas from an inlet of a blowing hole, and supply a control gas from an opening toward an axial center. This method has: a slag top-surface position measurement step, with the top surface of the molten iron measured in advance, measuring an arbitrary position in a top surface of the slag; a slag top-surface difference calculation of slag thickness difference between the measured top-surface positions of the molten iron and the slag; and a jetting condition adjustment step of, using the obtained slag thickness, adjusting a jetting condition of the gas jetted from the top-blowing lance into an appropriate range. The top-blown jetting condition is adjusted by comparing the slag thickness and the depth of a surface depression.

First claim

1 . A molten iron dephosphorization method that uses a top and bottom blown converter charged with molten iron and slag, and that, to perform dephosphorization of the molten iron by blowing an oxygen-containing gas from a top-blowing lance,
supplies the oxygen-containing gas as a main gas from an inlet of one or more blowing main holes that are disposed so as to extend through an outer shell of the top-blowing lance, and supplies a control gas from an opening disposed in an inner wall surface of the blowing main hole toward an axial center of the blowing main hole through a control gas supply passage, characterized in that
the method comprises:
a slag top-surface position measurement step of, with a position of a top surface of the molten iron having been measured in advance, continuously or intermittently measuring an arbitrary position in a top surface of the slag present on the molten iron;
a slag top-surface difference calculation step of calculating a slag thickness that is a difference between the measured top-surface positions of the molten iron and the slag; and
a jetting condition adjustment step of, using the obtained slag thickness, adjusting a jetting condition of the oxygen-containing gas jetted from the top-blowing lance into an appropriate range.

2 . A molten iron dephosphorization method that uses a top and bottom blown converter charged with molten iron and slag, and that, to dephosphorize the molten iron by blowing an oxygen-containing gas from a top-blowing lance,
supplies the oxygen-containing gas as a main gas from an inlet of one or more blowing main holes that are disposed so as to extend through an outer shell of the top-blowing lance, and supplies a control gas from an opening disposed in an inner wall surface of the blowing main hole toward an axial center of the blowing main hole through a control gas supply passage, characterized in that
the method comprises:
an initial slag thickness calculation step of, with a position of a top surface of the molten iron and a position of a top surface of the slag having been measured in advance, calculating a slag thickness;
a slag thickness change calculation step of continuously measuring the position of the top surface of the slag during blowing and calculating changes in the slag thickness; and
a jetting condition adjustment step of, using the obtained initial slag thickness and changes in the slag thickness, adjusting a jetting condition of the oxygen-containing gas jetted from the top-blowing lance into an appropriate range.

3 . The molten iron dephosphorization method according to claim 1 , wherein
the oxygen-containing gas jetted from the top-blowing lance penetrates through the slag on the molten iron and reaches the top surface of the molten iron.

4 . The molten iron dephosphorization method according to claim 3 , wherein
a depth of a depression in the molten iron made by the oxygen-containing gas having penetrated through the slag is less than 10% of the thickness of the slag.

5 . The molten iron dephosphorization method according to claim 1 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas supply pressure and a main gas supply pressure.

6 . The molten iron dephosphorization method according to claim 1 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas flow rate and a main gas flow rate.

7 . The molten iron dephosphorization method according to claim 2 , wherein
the oxygen-containing gas jetted from the top-blowing lance penetrates through the slag on the molten iron and reaches the top surface of the molten iron.

8 . The molten iron dephosphorization method according to claim 7 , wherein
a depth of a depression in the molten iron made by the oxygen-containing gas having penetrated through the slag is less than 10% of the thickness of the slag.

9 . The molten iron dephosphorization method according to claim 2 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas supply pressure and a main gas supply pressure.

10 . The molten iron dephosphorization method according to claim 3 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas supply pressure and a main gas supply pressure.

11 . The molten iron dephosphorization method according to claim 4 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas supply pressure and a main gas supply pressure.

12 . The molten iron dephosphorization method according to claim 7 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas supply pressure and a main gas supply pressure.

13 . The molten iron dephosphorization method according to claim 8 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas supply pressure and a main gas supply pressure.

14 . The molten iron dephosphorization method according to claim 2 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas flow rate and a main gas flow rate.

15 . The molten iron dephosphorization method according to claim 3 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas flow rate and a main gas flow rate.

16 . The molten iron dephosphorization method according to claim 4 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas flow rate and a main gas flow rate.

17 . The molten iron dephosphorization method according to claim 7 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas flow rate and a main gas flow rate.

18 . The molten iron dephosphorization method according to claim 8 , wherein
an adjustment of the jetting condition of the top-blowing lance is an adjustment of a ratio between a control gas flow rate and a main gas flow rate.

Assignees

• Jfe Steel Corp

Inventors

• Murakami Yumi
• Oda Nobuhiko
• Negishi Hidemitsu
• Kawabata Ryo
• Kikuchi Naoki
• Fujii Yusuke

Classifications

• C21C1/02 Primary

  Dephosphorising or desulfurising · CPC title

• C21C7/064

  Dephosphorising; Desulfurising · CPC title

• C21C5/35

  Blowing from above and through the bath · CPC title

• Y02P10/25

  Process efficiency · CPC title

• C21C5/4673

  Measuring and sampling devices · CPC title