Method for reducing salt usage in aluminum recycling

Patent metadata

Field	Value
Publication number	US-10669609-B2
Application number	US-201715845113-A
Country	US
Kind code	B2
Filing date	Dec 18, 2017
Priority date	Dec 18, 2017
Publication date	Jun 2, 2020
Grant date	Jun 2, 2020

Abstract

A method of melting an aluminum charge having no more that 4% salt by mass, including during a melting phase, introducing fuel and oxidant via a burner operating at a first firing rate, the fuel and oxidant reacting to form a combustion zone above the aluminum charge, terminating the melting phase and commencing a transition phase when the aluminum charge is nearly completely molten, during the transition phase, reducing the firing rate of the burner to a second firing rate lower than the first firing rate, introducing a non-oxidizing gas at a first velocity to form a non-oxidizing zone between the combustion zone and the aluminum charge, and allowing the aluminum charge to become completely molten, and terminating the transition phase and commencing a tapping phase after the aluminum charge has become completely molten, and during the tapping phase, pouring the molten aluminum charge out of the furnace.

First claim

The invention claimed is:

1. A method of melting in a furnace an aluminum charge comprising no more that 4% salt on a mass basis, the method comprising:
during a melting phase, introducing fuel and oxidant into the furnace via a burner operating at a first firing rate, the fuel and oxidant reacting to form a combustion zone above the aluminum charge;
terminating the melting phase and commencing a transition phase when the aluminum charge is nearly completely molten;
during the transition phase:
reducing the firing rate of the burner to a second firing rate that is lower than the first firing rate,
introducing a non-oxidizing gas into the furnace at a first velocity to form a non-oxidizing zone between the combustion zone and the aluminum charge; and
allowing the aluminum charge to become completely molten; and

terminating the transition phase and commencing a tapping phase at a time after the aluminum charge has become completely molten; and
during the tapping phase, pouring the molten aluminum charge out of the furnace.

2. The method of claim 1 , further comprising the steps of:
after the transition phase and before the tapping phase, commencing a stirring phase, comprising the steps of:
halting the flow of non-oxidizing gas;
stirring the molten aluminum charge; and
resuming the flow of non-oxidizing gas at a second velocity.

3. The method of claim 2 , wherein the molten aluminum charge is stirred by one or both of an implement attached to a construction vehicle and rolling the furnace about an axis.

4. The method of claim 1 , further comprising, during the tapping phase, flowing the non-oxidizing gas at a third velocity over the molten aluminum charge while pouring the molten aluminum charge out of the furnace.

5. The method of claim 1 , wherein the non-oxidizing gas is an inert gas, and wherein the non-oxidizing zone is an inert zone.

6. The method of claim 5 , wherein the inert gas is selected from the group consisting of nitrogen, argon, and a mixture of nitrogen and argon.

7. The method of claim 1 , wherein the flow of non-oxidizing gas is introduced at an angle complementary to an angle of the flow of fuel and oxidant, such that the flow of the non-oxidizing gas and the flow of the fuel and oxidant will not substantially disturb one another.

8. The method of claim 7 , wherein the flow of non-oxidizing gas forms a blanket above the molten aluminum.

9. The method of claim 1 , wherein the first velocity of the non-oxidizing gas flow is at least 400 m/s.

10. The method of claim 2 , wherein the second velocity of the non-oxidizing gas flow is equal to or less than the first velocity.

11. The method of claim 4 , wherein the third velocity of the non-oxidizing gas flow is equal to or less than the first velocity and is at least 200 m/s.

12. The method of claim 4 , further comprising, during the tapping phase:
cooling the flow of non-oxidizing gas; and
convectively cooling the molten aluminum with the flow of non-oxidizing gas.

Assignees

• Air Prod & Chem

Inventors

• Lawrence Martin
• Tlamicha Petr

Classifications

• F27B3/22

  Arrangements of air or gas supply devices · CPC title

• F27B7/06

  adapted for treating the charge in vacuum or special atmosphere · CPC title

• F27B3/28

  Arrangement of controlling, monitoring, alarm or the like devices · CPC title

• C22B9/006

  with use of an inert protective material including the use of an inert gas · CPC title

• C22B21/0084 Primary

  melting and handling molten aluminium (C22B21/02, C22B21/04 and C22B21/06 take precedence) · CPC title