Hot Metal Production from DRI with Electric Arc Heating

Patent metadata

Field	Value
Publication number	US-2023287528-A1
Application number	US-202318118355-A
Country	US
Kind code	A1
Filing date	Mar 7, 2023
Priority date	Mar 11, 2022
Publication date	Sep 14, 2023
Grant date	—

Abstract

According to embodiments, disclosed is a method and system to maintain the soft and sparse slag characteristic favorable for an electric arc to efficiently transfer the energy to molten iron with the power input per furnace area higher than 600 KW/m2 while keeping FeO amount less than 5% in the slag and carbon amount higher than 2.5% in the product hot metal at a DRI melting furnace.

First claim

What is claimed is:

1 . A method to maintain a soft and sparse slag characteristic favorable for an electric arc furnace to efficiently transfer energy to molten iron with a power input per furnace area higher than 600 KW/m2 while maintaining a FeO amount less than 5 wt. % in the slag and a carbon amount higher than 2.5 wt. % in a product hot metal at a direct reduced iron (DRI) melting furnace, comprising:
providing an electric DRI melting furnace as an electric arc furnace and including a plurality of electrodes for electric arc heating; charging the DRI to the DRI melting furnace through a chute; charging lumpy carbonaceous material fed along with the DRI; forming a slag layer comprising slag and forming a layer of molten iron below the slag layer; providing at least one oxygen injection nozzle for injection of oxygen; injecting the oxygen into the slag layer not penetrating the slag or reaching the molten iron from the at least one oxygen injection nozzle; adjusting oxygen flow rate to stabilize current fluctuation for each electrode; discharging the slag through a slag door or a slag tap hole located at an intermediate elevation of a side wall of the DRI melting furnace; and discharging the product hot metal through a tap hole located at a bottom or lower portion of the DRI melting furnace; wherein the method maintains the soft and sparse slag characteristic favorable for the electric arc furnace to efficiently transfer energy to the molten iron with a power input per furnace area higher than 600 KW/m2 while maintaining the FeO amount less than 5 wt. % in the slag and the carbon amount higher than 2.5 wt. % in the product hot metal at the DRI melting furnace.

2 . The method of claim 1 , comprising providing multiple injection nozzles circumferentially laid out around the furnace and wherein the oxygen is injected with a sub-sonic gas velocity toward the electrodes from the injection nozzles.

3 . The method of claim 1 , wherein the oxygen flow rate is controlled to maintain a noise level below 90 dB at the DRI melting furnace.

4 . The method of claim 1 , wherein the amount of the lumpy carbonaceous material is more than 30 kg of carbon left in the slag per 1 ton of molten iron.

5 . The method of claim 1 , wherein pulverized carbonaceous material or natural gas is injected in the slag together with the oxygen.

6 . The method of claim 5 , wherein the amount of carbon or natural gas is equal or more than the stoichiometric amount to the oxygen in the combustion reaction forming CO2.

7 . The method of claim 1 , wherein the elevation of the slag upper portion is maintained above the elevation of the slag tapping hole or the bottom end of the slag door while the slag is discharged, to prevent the carbonaceous material floating in the liquid slag from being discharged with the slag from the DRI melting furnace.

8 . The method of claim 1 , wherein combustible gas such as natural gas, reducing gas or inert gas such as nitrogen is injected to stir the molten iron to enhance mixing and replace some of the carbonaceous material fed along with the DRI to efficiently carburize the molten iron.

9 . The method of claim 1 , wherein the molten iron is stirred by an electromagnetic stirrer during the hot metal production.

10 . The method of claim 1 , wherein the DRI is made from iron ore containing an iron content <65 wt. %.

11 . A method of producing a product hot metal from DRI using electric arc heating comprising:
charging the DRI along with lumpy carbonaceous material to an electric DRI melting furnace through at least one chute; forming a slag layer comprising slag and forming a layer of molten iron below the slag layer; injecting oxygen into the slag layer not penetrating the slag or reaching the molten iron from the multiple injection nozzles circumferentially laid out; discharging the slag through a slag door or a slag tap hole located at an intermediate elevation of a side wall of the furnace; and discharging the product hot metal through a tap hole located at a bottom or lower portion of the DRI melting furnace; wherein the method further comprises maintaining a soft and sparse slag characteristic favorable for an electric arc to efficiently transfer energy to the molten iron with a power input per furnace area higher than 600 KW/m2 while maintaining a FeO amount less than 5 wt. % in the slag and a carbon amount higher than 2.5 wt. % in the product hot metal at the DRI melting furnace.

12 . A system configured to maintain a soft and sparse slag characteristic favorable for an electric arc furnace to efficiently transfer energy to molten iron with a power input per furnace area higher than 600 KW/m2 while maintaining an FeO amount less than 5 wt. % in the slag and a carbon amount higher than 2.5 wt. % in a product hot metal at direct reduced iron (DRI) melting furnace, the system comprising:
an electric DRI melting furnace as an electric arc furnace and including a plurality of electrodes for electric arc heating; a chute configured to charge therethrough the DRI along with lumpy carbonaceous material to the DRI melting furnace through the chute; wherein the system is configured to form a slag layer comprising slag and a layer of molten iron below the slag layer; at least one oxygen injection nozzle configured to inject oxygen into the slag layer not penetrating the slag or reaching the molten iron from the at least one oxygen injection nozzle; an oxygen adjustor configured to adjust oxygen flow rate to stabilize current fluctuation for each electrode; a slag door or a slag tap hole located at an intermediate elevation of a side wall of the DRI melting furnace configured to discharge the slag; and a tap hole located at a bottom or lower portion of the DRI melting furnace configured to discharge the product hot metal; wherein the system is configured to maintain the soft and sparse slag characteristic favorable for the electric arc furnace to efficiently transfer energy to the molten iron with a power input per furnace area higher than 600 KW/m2 while maintaining the FeO amount less than 5 wt. % in the slag and the carbon amount higher than 2.5 wt. % in the product hot metal at the DRI melting furnace.

13 . The system of claim 12 , comprising multiple injection nozzles circumferentially laid out around the furnace and wherein the oxygen is configured to be injected with a sub-sonic gas velocity toward each electrode from the injection nozzles.

14 . The system of 12 , wherein the amount of the lumpy carbonaceous material is more than 30 kg of carbon left in the slag per 1 ton of molten iron.

15 . The system of claim 12 , wherein pulverized carbonaceous material or natural gas is configured to be injected in the slag together with the oxygen.

16 . The system of claim 15 , wherein the amount of carbon or natural gas is equal or more than the stoichiometric amount to the oxygen in the combustion reaction forming CO2.

17 . The system of claim 12 , wherein the elevation of the slag upper portion is maintained above the elevation of the slag tapping hole or the bottom end of the slag door while the slag is discharged, to prevent the carbonaceous material floating in the liquid slag from being discharged with the slag from the DRI melting furnace.

18 . The system of claim 12 , wherein combustible gas such as natural gas, reducing gas or inert gas such as nitrogen is configured to be injected to stir the molten iron to enhance mixing and replace some of the carbonaceous material fed along with the DRI to efficiently c

Assignees

• Midrex Technologies Inc
• Kobe Steel Ltd

Inventors

• Michishita Haruyasu
• Tokuda Koji
• Mimura Tsuyoshi
• Fujiwara Katsuma

Classifications

• C21B2100/64

  Controlling the physical properties of the gas, e.g. pressure or temperature · CPC title

• C21B2100/66

  Heat exchange · CPC title

• C21B2100/26

  by adding additional fuel in recirculation pipes · CPC title

• C21B2100/22

  by reforming · CPC title

• C21B2100/44

  Removing particles, e.g. by scrubbing, dedusting · CPC title