Claims
- 1. A process for removing from aluminum scrap coatings having volatile components, said process comprising: passing the aluminum scrap through a kiln, the interior of which is isolated from the surrounding atmosphere; directing an airstream through the interior of the kiln; heating the airstream, before it enters the kiln, to a temperature in excess of that required to volatilize the coating and contemporaneously reducing the oxygen content of the airstream to below that necessary for supporting combustion of the coating within the kiln, so that the airstream within the kiln will volatilize the volatile components of the coating, but will not ignite those components; extracting heat from the airstream before it enters the kiln to maintain the temperature of the airstream where it enters the kiln substantially constant at a magnitude high enough to volatilize the coating, yet below the melting point of aluminum; and varying the mass flow of the airstream through the kiln to maintain the temperature of the airstream where it leaves the kiln substantially constant, whereby the airstream accommodates variations in the mass flow of the scrap and the nature of the scrap within the kiln.
- 2. The process according to claim 1 wherein the step of varying the mass flow includes diverting a portion of the airstream after it is heated, and controlling the portion so diverted.
- 3. The process according to claim 1 wherein the step of directing the airstream into through a kiln includes forcing it into the kiln with a fan; and the step of varying the mass flow includes varying the speed of the fan.
- 4. A process for removing coatings having volatile components from aluminum scrap, said process comprising: generating an airstream; directing the airstream into the interior of a kiln; passing through the kiln aluminum scrap having a coating provided with volatile components; heating the airstream before it enters the kiln; maintaining the oxygen content of the airstream at less than that of ambient air; where the airstream enters the kiln, maintaining the temperature of the airstream substantially constant and high enough to volatilize the coating without melting the aluminum, wherein the coating volatilizes in the kiln and enters the airstream; and without substantially altering the oxygen content of the airstream, varying the mass flow of the airstream through the kiln to maintain the temperature of the airstream where it leaves the kiln substantially constant, whereby the airstream accommodates variations in the mass flow of the scrap through the kiln and variations in the nature of the scrap within the kiln.
- 5. The process according to claim 4 wherein the step of maintaining the temperature of the airstream substantially constant where it enters the kiln includes extracting heat from the airstream before it enters the kiln and after it is heated.
- 6. The process according to claim 5 wherein the step of generating the airstream includes directing the airstream through a fan.
- 7. The process according to claim 6 wherein the step of varying the mass flow of the airstream includes varying the speed of the fan.
- 8. The process according to claim 5 wherein the step of heating the airstream includes supplying combustion air to the airstream and igniting a combustible substance within the airstream.
- 9. The process according to claim 8 and further comprising using the heat extracted from the airstream to heat the combustion air.
- 10. The process according to claim 4 and further comprising isolating the kiln from ambient air so that its oxygen content remains less than that of ambient air.
RELATED APPLICATION
This application is a division of application Ser. No. 07/401,795, filed Sep. 1, 1989, U.S. Pat. No. 5,059,116, which is a continuation-in-art of application Ser. No. 07/285,637, filed Dec. 16, 1988, now abandoned.
US Referenced Citations (9)
Foreign Referenced Citations (1)
Number |
Date |
Country |
1578689 |
Nov 1980 |
GBX |
Non-Patent Literature Citations (1)
Entry |
Waste Heat Recovery in Aluminum Scrap Recycling pp. 191-199. |
Divisions (1)
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Number |
Date |
Country |
Parent |
401795 |
Sep 1989 |
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Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
285637 |
Dec 1988 |
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