Method for controlling nitrogen in steelmaking by spraying hydrogen containing plasma

Patent metadata

Field	Value
Publication number	US-12234521-B2
Application number	US-202418670631-A
Country	US
Kind code	B2
Filing date	May 21, 2024
Priority date	May 31, 2023
Publication date	Feb 25, 2025
Grant date	Feb 25, 2025

Abstract

The application provides a method for controlling nitrogen in steelmaking by spraying hydrogen containing plasma, including: using a mixture of hydrogen rich gas and argon gas to generate hydrogen plasma for denitrification of molten steel during at least one of arc furnace smelting, ladle refining, VOD refining, and RH refining. The method for controlling nitrogen in steelmaking by spraying hydrogen containing plasma provided in the application can effectively remove nitrogen from the molten steel by spraying a mixture of argon gas and hydrogen rich gas into the molten steel through a hollow electrode and plasma torch, reducing electrode consumption and electricity consumption per ton steel, and also reducing arc radiation heat loss, improving heating rate, thereby shortening smelting time and reducing production costs.

First claim

What is claimed is:

1. A method for controlling nitrogen in steelmaking by spraying hydrogen containing plasma, comprising:
performing arc furnace smelting, ladle refining and Vacuum Oxygen Decarburization (VOD) refining, alternatively performing arc furnace smelting, ladle refining and Ruhstahl Hausen (RH) refining;
when performing at least one of the arc furnace smelting, the ladle refining, the VOD refining, and the RH refining, using a mixture of hydrogen rich gas and argon gas to generate hydrogen plasma for denitrification of molten steel;
wherein the arc furnace smelting comprises: spraying argon gas into the furnace through a hollow graphite electrode, with a gas flow rate 10-30 NL/min/t, an inlet gas pressure 0.1-1.0 MPa, and a bottom blown argon gas flow rate of 1-5 NL/min/t; before performing power transmission and forming a molten pool, spraying the mixture of hydrogen rich gas and argon gas into the molten steel through the hollow graphite electrode, with a proportion of hydrogen rich gas of 5%-80%, a flow rate of 10-30 NL/min/t, an inlet gas pressure 0.1-1.0 MPa, and the bottom blown argon flow rate of 1-5 NL/min/t; from forming the molten pool to completely melting, spraying the mixture of hydrogen rich gas and argon gas into the molten steel through the hollow graphite electrode, with a proportion of hydrogen rich gas of 5%-80%, a flow rate of 20-30 NL/min/t, an inlet gas pressure 0.1-1.0 MPa, and the bottom blown argon flow rate of 2-6 NL/min/t; from completely melting to steelmaking, spraying the mixture of hydrogen rich gas and argon gas into the molten steel through the hollow graphite electrode, with a proportion of hydrogen rich gas of 10%-80%, a flow rate of 10-20 NL/min/t, an inlet gas pressure 0.1-1.0 MPa, and the bottom blown argon gas flow rate of 2-6 NL/min/t; during steelmaking, stopping the hollow graphite electrode from blowing gas;
the ladle refining comprises: adding refining slag after the arc furnace smelting to cover a molten steel surface, preventing the molten steel from absorbing nitrogen; after moving a ladle car to a refining station, descending the hollow graphite electrode to 30-50 cm above a molten steel level, and introducing pure argon gas with a gas flow rate 10-20 NL/min/t, and an inlet gas pressure 0.1-0.6 MPa; during desulfurization of the molten steel, introducing pure argon gas blowing from a bottom nozzle to cause stirring of the molten steel with a gas flow rate 25-30 NL/min/t and an inlet gas pressure 0.1-0.6 MPa; after desulfurization under stirring, adding slag material, deoxidizer, and alloy to the ladle, introducing pure argon gas into the hollow graphite electrode, with a gas flow rate 5-10 NL/min/t and an inlet gas pressure 0.1-0.6 MPa; when performing power transmission for slagging, introducing the mixture of hydrogen rich gas and argon gas into the hollow graphite electrode, with a proportion of hydrogen rich gas of 5-80%, a total gas flow rate of 5-10 NL/min/t, and an inlet gas pressure 0.1-0.6 MPa; after slagging, the slag covers the arc as foam, the proportion of hydrogen rich gas is 5-80%, with a total gas flow 20-30 NL/min/t, and the inlet gas pressure is 0.4-0.5 MPa; after power transmission, lifting the hollow graphite electrode 30-50 cm above the molten steel, introducing pure argon gas, with a gas flow rate 10-20 NL/min/t and an inlet gas pressure 0.1-0.6 MPa; after refining the ladle, stopping the hollow graphite electrode from blowing gas, lifting the electrode to a highest limit, and moving the ladle car to a hanging position;
the VOD refining process comprises: adjusting the bottom blown gas flow rate to 200 NL/min when vacuuming to 20-25 kPa, and simultaneously turning on a plasma torch to spray the mixture of hydrogen rich gas and argon gas, with a total flow rate of the mixture of 1-8 NL/min/t, a proportion of the hydrogen rich gas of 5%-80%, a total gas source pressure of 0.1-0.5 MPa, and a spraying time of 2-3 minutes; vacuuming to 3-10 kPa, stirring by bottom blowing, increasing the bottom blown gas flow rate to 500 NL/min, and keeping parameters of the plasma torch for spraying the mixture of hydrogen rich gas and argon gas; vacuuming to below 67 Pa, increasing the bottom blown gas flow rate to 800 NL/min, increasing the mixture flow rate of hydrogen rich gas and argon sprayed by the plasma torch to 2-10 NL/min/t, increasing the proportion of hydrogen rich gas to 20%-80%, and increasing the total gas source pressure to 0.1-0.5 MPa, and spraying for 10-15 minutes; stopping the plasma torch from spraying, keeping the bottom blown gas flow rate unchanged, keeping the vacuum degree below 67 Pa, keeping the pressure for 5-10 minutes, and removing hydrogen from the molten steel;
the RH refining process comprises: vacuuming to 7-10 kPa, turning on the plasma torch to blow the mixture of hydrogen rich gas and argon gas for pre-denitrification, with a total flow rate of 1-8 NL/min/t of the mixture, with the proportion of hydrogen rich gas of 5%-80%, a total gas source pressure 0.1-0.5 MPa, and processing for 2-3 minutes; vacuuming to below 3 kPa, spraying the mixture of hydrogen rich gas and argon gas by the plasma torch, keeping the spraying parameters unchanged, and performing initial denitrification for 3-5 minutes; vacuuming to below 67 Pa, spraying the mixture of hydrogen rich gas and argon gas into the plasma torch, increasing the total gas flow rate to 2-10 NL/min/t, and increasing the proportion of hydrogen rich gas to 20%-80%, performing deep denitrification while keeping the total gas source pressure unchanged, and processing for 10-15 minutes; stopping the plasma torch from spraying, keeping the vacuum degree below 67 Pa, further processing for 5-10 minutes, and removing hydrogen from the molten steel.

2. The method for controlling nitrogen in steelmaking by spraying hydrogen containing plasma according to claim 1 , wherein a pore size of the hollow graphite electrode is 2%-6% of an electrode diameter.

3. The method for controlling nitrogen in steelmaking by spraying hydrogen containing plasma according to claim 1 , wherein during refining the ladle, a temperature of the molten steel entering the ladle is 1580-1630° C.

4. The method for controlling nitrogen in steelmaking by spraying hydrogen containing plasma according to claim 1 , wherein after intensely stirring for desulfurization, adding deoxidizer to the ladle, then adding alloy, and finally adding slagging material, determining an addition amount of the deoxidizer based on incoming oxygen content, determining an addition amount of the alloy based on incoming composition, and the addition amount of the slagging material is 2-6 kg/t.

5. The method for controlling nitrogen in steelmaking by spraying hydrogen containing plasma according to claim 1 , wherein the hydrogen rich gas comprises one or more of CH 4 , H 2 , and coke oven gas after nitrogen removal.

Assignees

• Xuanhua Iron And Steel Group Co Ltd
• Univ Beijing Science & Technology
• Hbzx High Tech Co Ltd

Inventors

• Wang Hongbin
• Wei Guangsheng
• Zhu Rong
• Zhang Minghai
• Wang Jinlong
• Jia Jianping
• Yang Yongqiang
• Wang Jianzhong
• Zhao Yunxiang
• Li Xin
• Li Ceng
• Chang Huan

Classifications

• C21C7/10 Primary

  Handling in a vacuum · CPC title

• C21C7/064

  Dephosphorising; Desulfurising · CPC title

• C21C7/06

  Deoxidising, e.g. killing · CPC title

• C21C7/0087

  Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal · CPC title

• C21C5/52 Primary

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