CASE STUDY No. 9707
KEY WORDS ALUMINUM, SCRAP RECOVERY; ENERGY SAVINGS
AAP St. Marys Corporation
1100 McKinley Road
St. Marys, OH 45885
Contact: Tom Southard, Safety & Environmental Coordinator.
Tel: 419-394-7840, Ext. 247. Fax: 419-394-4776.
Summary
Scrap metal chips produced during the machining of cast aluminum automobile wheels are remelted at the factory instead of an off-site location, eliminating one complete melting cycle, reducing aluminum dross, and significantly lowering material and energy needs.
Action
AAP transforms aluminum ingot into finished cast aluminum wheels for both domestic and foreign automotive vehicles, Machining produces a significant volume of scrap aluminum chips--about 6 lbs. per wheel, or roughly 30% of the original casting. Previously, this scrap was sent to an off-site aluminum recycler where chips were melted to produce an aluminum ingot. On-site chip recycling eliminates the need to re-form ingot from chips, thus eliminating one complete melting cycle.
Estimated energy savings. AAP's melting process uses approximately 1,000 BTUs per pound of aluminum, and it is estimated the outside contractor's usage would be about the same. Since AAP remelts 9,960,000 pounds of chips per year, net annual energy savings amount to 9.96 billion BTUs of fuel. With annual production of 1.5 million wheels, savings can be expressed as 6,640 BTUs of fuel per product unit.
Estimated waste reduction. Dross is the waste byproduct of aluminum melting operations. AAP's new remelting process reduces dross--from 8% dross under the old process to 2% dross under the new in-plant recycling process. This can be expressed as 0.40 lbs. of waste dross reduction per wheel.
Payback
Material cost savings from AAP's process change are significant. By remelting chips in-house, AAP increases the yield from 92% to 98%. Monthly savings can be calculated with the following formula:
Process cost savings can be expressed as follows:
$133,630 less New Process Cost ($39,000) = $94,630 Process Cost Savings
