Laser Separates Aluminum by Alloy, Increases Scrap Value

DETROIT, Oct. 27 -- The Auto Aluminum Alliance, in conjunction with the US Department of Energy, has developed a recycling process that uses optical emission spectroscopy to improve the way the auto and aluminum industries recycle and sort scrapped automobiles. By using lasers to identify and recover metals from scrapped vehicles, researchers have demonstrated the ability to separate cast from wrought alloys, as well as the ability to separate wrought alloys from each other at commercially viable rates.
The techniques we're exploring will allow us to recapture more of the value and performance capability of the many high quality aluminum alloys that are used in our vehicles. Current separating techniques only allow us to separate aluminum from other materials in scrapped vehicles. The recovered aluminum is then recycled into castings. But the new techniques will enable us to separate cast aluminum from wrought and even differentiate between wrought alloys, said Jim Quinn, staff engineer, General Motors Corp. and chairman of the US Automotive Partnership, Automotive Metals and the US Council for Automotive Research.
Using Laser Induced Breakdown Spectroscopy (LIBS), the process uses a laser to first clean the surface of the particle by laser ablation, and then it uses a laser pulse to hit the same spot on the particle as it moves down a conveyer belt. This second laser pulse vaporizes a small amount of material from the metal's surface creating a small, highly luminescent plume of plasma, or ionized gas. To quantitatively determine the metal's chemical makeup, the plume is then analyzed by a technique called optical emission spectroscopy. Once the verification is made, the scrap is sorted by alloy on a piece-by-piece basis.