‘The first production car using aluminium unibody had an impressive 500 pounds weight savings over steel construction,’ observes Rick Comtois, ceo of Austin AI, Inc. Since that time aluminium became a dominant construction material of the car industry which, in fact, consequently requires specificity of the ELV recycling process.
Car wheels are a significant part of the total weight of aluminium dominant cars. They historically can be made from Fe, Mg, and wrought aluminium alloys. However the number one constituent in automotive wheels are cast aluminium based material. Cast aluminium wheels can vary in Si content from 5-6% up to 14-15%.
Very quick analysis
‘This variation makes the recycling process expensive as the addition of, or dilution using lower concentration Si additives, requires a lot of incremental furnace time,’ Comtois notes. Austin AI’s patented automated LIBS based sensor-sorter has solved this issue.
LIBS technology is well documented. It has the capabilities of other outer-shell electron spectroscopy such as arc/spark which are commonly used to certify—or advise—on the quality of any melt. Several key advantages of LIBS are non-contacting, very quick analysis time, and a full range of major/minor/trace elements.
If whole, used car wheels are desired to be sorted by alloy type, then commonly hand-held devices such as LIBS and XRF guns are used. ‘Even in the best of cases the wheels need some pretreatment for cleaning the analytical surface and seconds per analysis,’ Comtois says. ‘It is possible to run up to 1-2 wheels per minute in this manner optimally yeilding 1.5 tons per hour, per person.’
The AAI system automatically cleans, tests, and determine the wheel to pass or be rejected based on its chemistry. This can be done, including a residue reduction phase (abrasive cleaner), to easily yield about 10 times the throughput with no human interface. Used wheels, thus sorted, are capable of directly entering the wheel shredder followed by secondary furnace in-feed.
Make no mistake about the power of LIBS as an analytical tool. This technology is ’far superior’ to other sorting techniques such as X-ray (transmission or fluorescence), color sorting, or others; when considering sensitivity and timing.
The sorting process can be quite stringent. For example, one of our users has requirements beyond the Si content, such as very low Fe +/-0.15%, and Cu at +/-0.10%. ’When you imagine the wheels are moving for most applications using LIBS, this is a very impressive statement with regard to the latest advancement of the art,’ Comtois says.
‘The savings in fuel consumption per ton of output is a major savings by itself,’ according to Comtois. Labour, turnaround time, and tonnage throughput all dramatically feed to the bottom line of the secondary smelter. ‘In addition this generates a significant green impact to the smelter’s operations. It truly is this last point that reflects upon the sustainable nature for any secondary processor.’
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