Method For Reducing Salt Usage In Aluminum Recycling

Patent metadata

Field	Value
Publication number	US-2019185962-A1
Application number	US-201715845113-A
Country	US
Kind code	A1
Filing date	Dec 18, 2017
Priority date	Dec 18, 2017
Publication date	Jun 20, 2019
Grant date	—

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

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-type 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.

13 . A system for melting an aluminum charge comprising no more than 4% salt on a mass basis in a furnace having a door, comprising:
a burner mounted in the door of the furnace, the burner being configured to introduce fuel and oxidant into the furnace to form a combustion zone above the aluminum charge; a lance configured to introduce a non-oxidizing gas into the furnace to form a non-oxidizing zone between the combustion zone and the aluminum charge; and a gas injector configured to introduce a non-oxidizing gas near the door of the furnace.

14 . The system of claim 13 , wherein the lance is mounted to the door of the furnace.

15 . The system of claim 14 , wherein the lance is configured to introduce non-oxidizing gas at a velocity of at least 400 m/s.

16 . The system of claim 14 , wherein the burner and the lance are oriented substantially perpendicular to the door.

17 . The system of claim 13 , wherein the gas injector comprises a manifold having one or more outlets, the one or more outlets configured to deliver a planar flow of non-oxidizing gas into the furnace when the door is open.

18 . The system of claim 17 , wherein the one or more outlets comprises a single, flat, wide outlet.

19 . The system of claim 17 , wherein the gas injector is configured to deliver the non-oxidizing gas at a velocity of at least 200 m/s.

20 . The system of claim 17 , wherein the gas injector is oriented such that the outlets introduce the flow of non-oxidizing gas substantially parallel to a top surface of the aluminum charge.

Assignees

• Air Prod & Chem

Inventors

• Lawrence Martin
• Tlamicha Petr

Classifications

• F27B14/08

  Details specially adapted for crucible or pot furnaces · CPC title

• F27B2014/0837

  Cooling arrangements · CPC title

• F27B14/14

  Arrangements of heating devices · CPC title

• C22B21/0084 Primary

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

• F27B7/36

  Arrangements of air or gas supply devices · CPC title