Knowedge Guide: Scrap Aluminum Recycling

Aluminum recycling and aluminum scrap recycling have developed into two distinct industries over the past several decades. Initially, the aluminum industry focused on producing large amounts of new metal aluminum products to reduce the overall price, thus becoming competitive with other materials and products. Over time, however, a secondary industry developed that focused on recycling the left-over scraps generated by primary aluminum products. Eventually, the secondary recycling industry began to focus on creating higher quality products from scrap aluminum, thus making recycled-material based products that could compete with new metal products, while new metal processes slowly moved toward collecting and recycling their process scraps.

Aluminum is extraordinarily light and corrosion resistant, making it one of the most widely used metals in various industries, including packaging, automotive, and construction. Additionally, it can easily be manipulated to produce differently shaped components, which has further enabled aluminum to be used in both small and large applications.

Recycling Aluminum

Recycled aluminum typically comes originates from one of two industries: municipal waste, such as waste generated from containers and packaging, and industrial scrap, such as sheets and films. Aluminum generated by these industries is often recycled and used to aid in the production of aluminum from bauxite. Other sources, such as waste generated by the transportation industry, (typically aluminum silicon or aluminum magnesium) and waste generated by electrical and construction applications, are used in the secondary aluminum recycling industry.

Before recycling, aluminum products are divided into two categories: aluminum by-products and aluminum scrap. Depending on the form of the aluminum, the recycling process will vary. First, the aluminum scrap must be sorted, which also involves several different processes.

When sorting scrap aluminum, any large components should be removed—electronic parts should be disassembled—and then passed along to recyclers. Aluminum beverage cans (abbreviated UBC for “used  beverage cans”) are sorted magnetically to weed out steel cans, then compacted with a baler—a device that employs three hydraulic rams—while smaller scrap is passed into a briquetter, which depends on rotating drums as a means of compression. Scrap is compressed to reduce the cost of shipping and make it easier to load the furnace.

Shredding is used in the case of large parts, such as aluminum from automotive applications. Hammer mills can shred very large components into easily sortable pieces, which can then be separated magnetically to sort the aluminum from other types of metal. Steel and iron can be sold to their appropriate mills, while the aluminum is further shredded and separated using different processes, such as heavy media separation, eddy current separation, and color sorting.

Despite the thorough sorting process, the metal content of aluminum is often difficult to discern. Therefore, the metal recovery (percentage of metal gained from the content of the scrap material) and the metal yield (percentage of metal gained from the mass of the scrap material) can vary. Sometimes the metal recovery is higher than the yield because of loss during melting or the presence of contaminants in the material. Typically, between 85-95 percent of metal can be recovered from the scrap.

For recycling used beverage cans and other forms of aluminum scrap, there are several furnaces that can be used. A reverberatory furnace is typically used for applications that contain at least 70 percent aluminum. Rotary furnaces, on the other hand, tend to function best with aluminum scrap that contains less than 70 percent aluminum. Sweat furnaces are effective in separating aluminum from iron, especially in composite components.

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