Method to protect the anode bottoms in batch DC electric arc furnace steel production

• US 6,693,947 B1
• Filed: 09/25/2002
• Issued: 02/17/2004
• Est. Priority Date: 09/25/2002
• Status: Expired due to Fees

• Current Assignee: D.L. Schroeder & Associates
• Original Assignee: D L Schroeder & Associates
• Inventors: Schroeder, David L.
• Primary Examiner(s): Hoang, Tu Ba
• Application Number:
  US10/255,736
• Time in Patent Office: 510 Days
• Field of Search: 373/60-63, 373/71-72, 373/79, 373/83, 373/84, 373/108, 373/2, 373/78, 266/45, 266/175, 266/233, 266/236, 266/240, 266/245, 266/44, 75/104.5, 75/103.9
• US Class Current: 373/79
• CPC Class Codes: C21C 2005/5235 with bottom electrodes
• CPC Class Codes: C21C 5/5229 in a direct current [DC] electric arc furnace
• CPC Class Codes: F27B 17/00 Furnaces of a kind not covered by any preceding group structural combinations of furnaces F27B19/02
• CPC Class Codes: F27B 3/085 Arc furnaces
• CPC Class Codes: F27B 3/19 Arrangements of devices for discharging
• CPC Class Codes: F27B 3/20 Arrangements of heating devices
• CPC Class Codes: F27B 3/225 Oxygen blowing
• CPC Class Codes: F27D 11/04 with direct passage of current through the material being heated
• CPC Class Codes: F27D 11/08 Heating by electric discharge, e.g. arc discharge
• CPC Class Codes: F27D 2003/164 Oxygen
• CPC Class Codes: F27D 2003/168 through a lance
• CPC Class Codes: F27D 3/1518 Tapholes
• CPC Class Codes: F27D 3/1554 for removing the slag from the surface of the melt
• CPC Class Codes: F27D 3/16 Introducing a fluid jet or current into the charge porous elements for gas flushing of molten metals B22D1/005

Abstract

A batch process for an electric arc furnace (1) to manufacture steel (10) includes the steps of providing an empty furnace having a bottom (14) and sides (16) and electrodes (2, 3); adding molten metal to the empty furnace; adding other necessary ingredients through charge openings (26); applying current to provide an arc (4) and supplying oxygen through an oxygen lance (6) to react and melt the contents of the furnace and form a top slag (9) and bottom molten metal/steel (10); and stopping the reaction and pouring out all the slag through a slag tap (5) and molten metal tap (32) to provide an empty furnace for the next batch run.

Claims

1. A process of operating a DC electric arc furnace in a batch process to produce steel, comprising adding raw iron bearing material carbon and lime to the furnace, applying current through at least one electrode to provide an arc and supplying oxygen to react and melt the materials to produce molten slag and molten carbon steel;

the improvement comprising pouring all the molten carbon steel produced to provide an empty furnace and then adding molten metal to the empty furnace before its next batch operation.

2. The process of claim 1, the improvement further comprising adding molten metal comprising hot metal.

3. The process of claim 1, the improvement further comprising use of at least one top electrode and at least one bottom electrode, where the added molten metal completely covers the bottom electrode height.

4. The process of claim 1, the improvement further comprising use of at least one top electrode and at least one bottom electrode, where the added molten metal level is over the bottom electrode.

5. The process of claim 1, the improvement further comprising heating the added molten metal at a temperature of from about 1400°

C. to about 1500°

C. in an associated channel induction furnace which operates between 1320°

C. and 1550°

C.

6. A process of operating a DC electric arc furnace containing top and bottom electrodes, in a batch process to produce molten carbon steel, comprising the steps:

(1) providing a furnace empty of molten metal and metal scrap, the furnace comprising a furnace bottom having upward sides and having at least one electrode having a top portion in the furnace bottom, at least one top electrode, an oxygen lance within the furnace, charging openings for raw materials; and

exists for slag and molten metal; and

then

(2) adding molten metal to cover at least 100% of the furnace bottom electrodes;

(3) adding solid raw iron bearing material, carbon and lime; and

(4) applying current through the top electrode to provide an arc and supplying oxygen through the oxygen lance to react and heat the raw materials, forming a molten metal layer on top of the furnace bottom and a covering top slag layer, where the reaction generates CO which, along with any carbon, reacts with O₂ to form a first rate of CO generation during which CO and CO₂ bubble through the slag; and

(5) stopping the reaction and pouring out all of the molten carbon steel and molten slag produced at a predetermined molten bath carbon concentration, to provide an empty furnace for the next batch process.

7. The process of claim 6, wherein the molten metal added in step (2) consists essentially of a higher carbon metal.

8. The process of claim 6, wherein the added molten metal added in step (2) is at a level over the bottom electrode.

9. The process of claim 6, wherein the molten metal added in step (2) has a temperature of from about 1400°

C. to 1500°

C.

10. The process of claim 6, wherein the molten metal added in step (2) is added from an associated channel induction furnace which operates at from about 1320°

C. to 1550°

C.

11. The process of claim 6, wherein step (4) is started within 3 minutes of step (2).

12. The process of claim 6, wherein the productivity of the DC furnace is increased by

the size of the hot metal heel;

2) the sensible heat in the hot metal heel;

3) the carbon in the hot metal heel.

13. The process of claim 6, wherein more heats can be made before replacement of the anode bottom.