|ALUMINUM/TIN CANS ECYCLING
Aluminum cans are collected in a variety of ways. In some countries, cans are returned through deposit schemes. With these systems you pay a deposit or fee when you purchase a full container. When the container is empty, you return it to a designated collection site and your fee is refunded. This collection method is very effective but the cost usually exceeds the recycling value for the containers. Buy back collection mechanisms is still very popular in many parts of the western hemisphere. People are offered money for aluminum cans that they collect and redeem at a recycling center or reverse vending machine. Most locations buy the cans by weight but some of the older systems pay for each can. Voluntary drop off locations are still in use in much of the EEC, and in more rural parts of the US. Many of these programs have been replaced by blue box programs, where a number of household recyclables are picked up at the curb and taken to large recycling facilities that sort and package the items for sale.
Recyclers can process aluminum cans in a number of ways. Small low volume processors will normally flatten cans and sell them to a nearby wholesaler. Larger operations will bale, densify or in some cases shred cans for shipment to aluminum consumers. The aluminum companies have defined specifications on how aluminum cans should be prepared.
How, exactly are the cans recycled ? After collection and processing the aluminum UBC ( Used Beverage Cans) are shipped by truck, railcar or sea container to smelting plants. The bales of cans are unloaded and tested for quality and moisture content. After inspection, the bales of cans are broken up in a shredder into small pieces. These shredded cans are then conveyed into a De-lacquering oven to remove the paint and residual moisture. The hot shredded aluminum is then passed over a small screen to remove and dirt and contaminants and fed directly into a reverbatory furnace. Heated to 1400 degrees Fahrenheit ( 650 Centigrade) the cans melt and blend in with the molten metal already in the furnace. A mixture of salt and KFl are added as a flux to help separate out any oxides (dross) that are skimmed off.
Molten aluminum is checked for proper chemistry and then tapped ( removed)
from the furnace and poured into large molds that cast sheet ingots. These
large rectangular ingots ( 20 to 40,000 lbs each) are allowed to cool and
harden. When they are needed, the top and bottom surface of the sheet ingot
( alloy 3105) is milled to a smooth surface in a process called "Scalping".
The scalped ingot is then passed between two giant steel rollers in a large
rolling mill. The sheet is passed through a few more times until it is
about 1/2 an inch (1.25 Cm) thick and maybe 1000 feet (300 meters)long.
This long sheet is then annealed to soften it and passed to a series of
rollers in a finishing mill where it acquires the necessary hardness and
thickness. The edges are trimmed in a slitter and the coil is rolled up
for shipment to a can manufacturer. The finished coil may be 2 miles (3
kilometers)long and made from over 1.2 million recycled cans.
If not properly recycled, an aluminum can will still be on the surface of the earth after 500 years. Aluminum recycling can reduce air pollution by 95%. It can save 90% to 95% of the energy required to manufacture aluminum from recycled aluminum cans than from aluminum core.
If each person recycles one aluminum can in each month, 1,750 to 3,500 gallons of gas can be saved
Tin can bundles are relatively low in value and are seldom imported. The value to recyclers depends mostly on the amount of freight it takes to reach a steel mill. Recycling processors were paid between $30 and $80 a ton for baled tin cans picked up at their facilities in 1998. Fortunately, this material is abundant and easy to process so the handling costs are fairly low. Because they are magnetic, they are sorted from other recylables automatically with a magnetic conveyor belt. These belts usually feed the steel directly into an automatic baling press which produce mill quality 1000 to 2000 lb bales that are ready for shipment.