Method for oxygen-blowing refining of molten iron and top-blowing lance

Patent metadata

Field	Value
Publication number	US-11293069-B2
Application number	US-201816955214-A
Country	US
Kind code	B2
Filing date	Nov 8, 2018
Priority date	Dec 22, 2017
Publication date	Apr 5, 2022
Grant date	Apr 5, 2022

Abstract

In a method for oxygen-blowing refining of molten iron, an oxygen-containing gas as a main supply gas is supplied from an inlet side of a blowing nozzle for the oxygen-containing gas passing through an outer shell of the top-blowing lance and blown from the blowing nozzle while a control gas is jetted toward inside of the blowing nozzle for at least part of a period of the oxygen-blowing refining from a spout arranged in a side face of the nozzle at a site where the cross-sectional area of the nozzle minimum takes the minimum in the axial direction of the nozzle or a neighborhood thereof so that at least part of the spout exists in each space formed by dividing into two portions by an arbitrary plane passing through a central axis of the nozzle.

First claim

The invention claimed is:

1. A method for oxygen-blowing refining of molten iron by blowing an oxygen-containing gas from a top-blowing lance onto molten iron charged in a reaction vessel to conduct oxygen-blowing refining of the molten iron, characterized in that
the oxygen-containing gas as a main supply gas is supplied from an inlet side of a blowing nozzle for the oxygen-containing gas passing through an outer shell of the top-blowing lance and blown from the blowing nozzle while a control gas is jetted toward inside of the blowing nozzle for at least a part of a period of the oxygen-blowing refining from a spout arranged in a side face of the blowing nozzle at a site where a cross-sectional area of the blowing nozzle takes the minimum in the axial direction of the blowing nozzle or a neighborhood thereof so that at least a part of the spout exists in each space formed by dividing the blowing nozzle into two by an arbitrary plane passing through a central axis of the blowing nozzle,
wherein the neighborhood of the site where the cross-sectional area of the blowing nozzle takes the minimum in the axial direction of the blowing nozzle is a site where the cross-sectional area of the blowing nozzle is not more than 1.1 times of the minimum cross-sectional area in the axial direction of the nozzle, and
wherein a pressure of the main supply gas at the inlet side of the blowing nozzle is made larger than an adequate expansion pressure Po satisfying the following equation (1):
Ae/At =(5 5/2 /6 3 )×( Pe/Po ) −5/7 ×[1−( Pe/Po ) 2/7 ] −1/2   (1),

wherein At is a minimum cross-sectional area of the blowing nozzle (mm 2 ), Ae is a cross-sectional area of an outlet of the blowing nozzle (mm 2 ), Pe is a pressure in an atmosphere at an outlet of the blowing nozzle (kPa) and Po is an adequate expansion pressure of the blowing nozzle (kPa).

2. The method for oxygen-blowing refining of the molten iron according to claim 1 ,
wherein the blowing nozzle is a straight nozzle having a straight portion continuous to the outlet of the blowing nozzle where the cross-sectional area is minimum and constant in the axial direction of the blowing nozzle or is a Laval nozzle having a widened portion continuous to a throat portion where the cross-sectional area takes the minimum in the axial direction of the blowing nozzle.

3. The method for oxygen-blowing refining of the molten iron according to claim 1 ,
wherein the spout comprises a plurality of spouts arranged at plural places in a side face of the blowing nozzle in a circumferential direction thereof and a product of a diameter of an introduction hole for the control gas toward the spouts and the number of the spouts n per one blowing nozzle is not less than 0.4 times of an inner diameter of the blowing nozzle at the site where the cross-sectional area of the blowing nozzle takes the minimum.

4. The method for oxygen-blowing refining of the molten iron according to claim 1 ,
wherein the spout is arranged in a slit form over the whole circumferential direction at a side face of the blowing nozzle and a length of the spout in the axial direction of the blowing nozzle is not more than 0.25 times of an inner diameter of the blowing nozzle at the site where the cross-sectional area of the blowing nozzle takes the minimum.

5. The method for oxygen-blowing refining of the molten iron according to claim 1 ,
wherein the amount of the control gas jetted toward inside of the blowing nozzle for at least part of a period of the oxygen-blowing refining is not less than 5% of a total amount of the control gas and the main supply gas supplied to the blowing nozzle.

6. The method for oxygen-blowing refining of the molten iron according to claim 1 ,
wherein a supply rate of the control gas is adjusted in accordance with a supply rate of the oxygen-containing gas blown from the top-blowing lance to the molten iron.

7. The method for oxygen-blowing refining of the molten iron according to claim 1 ,
wherein the supply rate of the control gas is varied with the progression of the oxygen-blowing refining of the molten iron.

8. The method for oxygen-blowing refining of the molten iron according to claim 1 ,
wherein the supply rate of the control gas is varied in accordance with a silicon concentration in the molten iron before the start of the oxygen-blowing refining.

9. The method for oxygen-blowing refining of the molten iron according to claim 1 ,
wherein the oxygen-containing gas is supplied as the main supply gas while the control gas is jetted in the blowing nozzle at a last stage of the oxygen-blowing refining after the supply of 85% of a total oxygen gas amount in the oxygen-containing gas fed in the oxygen-blowing refining.

10. The method for oxygen-blowing refining of the molten iron according to claim 1 ,
wherein the oxygen-containing gas is supplied as the main supply gas to the molten iron having a silicon concentration of not less than 0.40 mass % before the start of the oxygen-blowing refining while the control gas is jetted in the blowing nozzle at an initial stage of the oxygen-blowing refining before the supply of 20% of a total oxygen gas amount contained in the oxygen-containing gas fed in the oxygen-blowing refining.

11. A top-blowing lance for blowing an oxygen-containing gas to molten iron charged in a reaction vessel, characterized in that
a blowing nozzle for the oxygen-containing gas is provided so as to pass through an outer shell of the top-blowing lance;
a spout for jetting a control gas toward inside the blowing nozzle is arranged in a side face of the blowing nozzle at a site where a cross-sectional area of the blowing nozzle takes the minimum in the axial direction of the blowing nozzle or a neighborhood thereof so that at least part of the spout exists in each space formed by dividing the blowing nozzle into two by an arbitrary plane passing through a central axis of the blowing nozzle; and
introduction pathways for the control gas into plural spouts for the control gas arranged in plural directions in the circumferential direction of a side face of the blowing nozzle are communicated to each other in the top-blowing lance,
wherein the neighborhood of the site where the cross-sectional area of the blowing nozzle takes the minimum in the axial direction of the blowing nozzle is a site where the cross-sectional area of the blowing nozzle is not more than 1.1 times of the minimum cross-sectional area in the axial direction of the blowing nozzle, and
wherein the spout comprises a plurality of spouts arranged at plural places in the side face of the blowing nozzle in a circumferential direction thereof and the product of an inner diameter of a jetting nozzle for the control gas communicating with the spouts and number of the spouts n per one blowing nozzle is not less than 0.4 times of an inner diameter of the blowing nozzle corresponding to the minimum cross-sectional area of the blowing nozzle.

12. A top-blowing lance for blowing an oxygen-containing gas to molten iron charged in a reaction vessel,
characterized in that
a blowing nozzle for the oxygen-containing gas is provided so as to pass through an outer shell of the top-blowing lance, and
a spout for jetting a control gas toward inside the blowing nozzle is arranged in a slit form over the whole circumferential direction at a side face of the blowing nozzle at a site where a cross-sectional area of the blowing nozzle takes the minimum in the axial direction of the blowing nozzle or a neighborhood thereof,
wherein the neighborhood of the site where the cross-sectional area of the blowing nozzle takes the minimum in the axial direction of the blowing nozzle is a s

Assignees

• Jfe Steel Corp

Inventors

• Oda Nobuhiko
• Okuyama Goro
• Amano Shota
• Nakase Kenji
• Takahashi Yukio
• Hino Yuta
• Kikuchi Naoki
• Miki Yuji

Classifications

• C21C5/32 Primary

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

• C21C5/4606 Primary

  Lances or injectors · CPC title