Primary Aluminium History: People often think of aluminum as a cheap and plentiful metal, but 130 years ago aluminum was considered rare and expensive. According to the book “Chemical Principles,” refining aluminum from bauxite was so costly in the 19th century that the Washington Monument was given an aluminum tip to symbolize its value. In 1886, chemist Mr. Charles Martin Hall invented a cheaper way to refine aluminum from bauxite. The method he discovered is still in use today. Despite its convenience, however, the Hall process uses a considerable amount of energy.(See reference 4).
Why Aluminium should be Recycled: Aluminium is 100% recyclable and experiences no loss of properties or quality during the recycling process. Recycling aluminium also uses only 5% of the energy used to create new Aluminium and emits only 5% of the greenhouse gases. It is for these reasons that approximately 75% of the aluminium ever produced is still in use today by recycling method.
Recycling Method: Aluminium recycling is the process by which scrap aluminium can be reused in products after its initial production. The process involves simply re-melting the metal, which is far less expensive and energy intensive than creating new Aluminium from its Bauxite Ore.
Success of Aluminium Recycling: Aluminum production has been ongoing for over a century and is still going strong. One of the key factors in the success of aluminum is its recyclability. In fact, recycling has proven so valuable—both economically and ecologically—that recovery and recycling has become its own industry, and a highly successful one.
While UBC (Used Beverages Can) are the most visible part of the aluminum recycling story, they are far from the whole story. In fact, UBC recycling typically amounts to less than 30 percent of the tonnage of aluminum consumer products that are recycled.
The growth of the market for recycled aluminum is due in large measure to economics. Today, “Aluminium Recycling” is cheaper, faster, and more energy efficient & it achieves higher recovery rate of aluminum than ever before. In addition, to achieve a given output of ingot, recycled aluminum requires only about 10 percent of the capital equipment compared with primary aluminum.
Importance of Recycling Aluminum (UBC) Cans:
Saving Energy & Achieving Carbon Credit
According to the Aluminum Association, an industry trade group, recycling just one can saves the amount of energy it takes to watch the Super bowl — in other words, the amount of energy needed to power a television for three hours.(See Reference 4)
Reducing Greenhouse Gas Emissions
In the Hall process, current passes through graphite electrodes submerged in molten alumina, or Al2O3. The carbon in the graphite electrodes reacts with the oxygen in the molten alumina to yield carbon dioxide. Although pure aluminum is isolated in the process, the amount of carbon dioxide released is considerable — more than 1 ton of carbon dioxide for every ton of aluminum produced (see References 1). According to Waste Online, recycling aluminum releases only 5 percent of the CO2 required to refine fresh aluminum from bauxite. This way you will get carbon Credit by adopting recycling process.
Reducing Waste & Mining Impacts
According to the EPA, Americans threw out 3.4 million tons of aluminum in 2009 — roughly 1.4 percent of the total waste stream. Moreover, the more aluminum recycled, the less manufacturers need to produce. Production of aluminum necessitates extraction of bauxite ore, and mining also has environmental impacts. Typically bauxite is strip-mined, meaning the soil atop the deposit is removed; in the process, the vegetation at the site is destroyed. (See References 3,4)
Economic Value of Recycled Aluminum
Recycled aluminum is a valuable commodity, so most recycling centers will accept your used cans. Moreover, aluminum can be recycled indefinitely — with no limit on the number of times the metal can be reused. According to the Aluminum Association, this property of aluminum gives it an extraordinarily high value as scrap (see References). According to Waste Online, aluminum is more cost-effective to recycle than any other metal (see References 2). The EPA notes that aluminum is easy to recycle, so there’s a wide market for the recycled product.
Aluminium Recycling Process
The aluminum recycling process is fairly straightforward in its major steps. Aluminum cans (UBC) recycling, for example, is a closed-loop process, which means the new product at the end of the recycling process is the same as the source product. It goes like this:
- The consumer throws aluminium beverage cans and foil into a recycle bin.
- All UBC (Used Beverage Cans) are baled and formed in compact shape and size for ease of logistics.
- In the treatment plant the aluminium is sorted and cleaned ready for reprocessing
- The cans are shredded into small pieces and fed into a Decoater Dryer Machine to remove paint coating available on surface area of the UBC metal shreds.
- It then goes through a re-melt process and turns into molten Aluminium Metal.
- The molten metal from the furnace is molded and cooled into rectangular or in other type of ingots.
- The ingots are sent to other process or flattened into thin sheets, which are then used to make new cans.
How the process works
1.) The Loading Conveyor:
Aluminium UBC arrives at the recycling plant in large blocks, or bales. These bales are loaded onto a conveyor, which takes them to the shredder.
2.) The Shredder:
The shredder chops the cans into small pieces. The pieces are about the size of a 50p coin. This is so that it is easier to remove all the paint and coatings used to decorate and protect the can. It also makes the metal melt faster in the furnace.
3.) The Magnetic Separator:
Shredded pieces of UBC are passed under a very powerful magnet which removes any traces of steel or the magnetic impurities. Steel or iron impurities are magnetic hence they can be separated from the aluminium using this powerful magnet.
4.) Rotary Decoater:
The aluminium shreds move along the conveyor into the Decoater. Here the paint decoration is removed from the shredded cans. The decoater blows hot air through the shreds and the paint and coatings vaporise. The decoating process also warms the shreds up, so that they melt faster when they reach the furnace. The hot gases are removed and cleaned by passing into the after burn chamber. It saves 95% of the greenhouse gas emissions compared to the primary, or smelting, process.
5.) Side well Melting Furnace:
The decoated shreds are fed into the furnace. The furnace is heated to 800°C – this is a low melting point for a metal. These furnaces are the latest ones with capacities ranging from 10 to 100 T. The charging of the light scrap is done in the side well, while fuel-fired burners give the heat input in the main well. The metal pump circulates the hot metal from main well to side well & also allows gas injection.
Vortex Generator: This new technology. Vortex generator or elctro-magnetic pump further improves the melting rate, reduce melt loss, improves alloy dissolution rate, reduce inclusion & gas contamination. Light scrap in the form of chips can be charged through a conveyor continuously in the vortex created.
Holding Furnace: The molten aluminium is transferred to another furnace. This ‘Holding furnace’ is where the metal waits to be cast into ingots. You can add various metals like Magnesium, Silicon, Copper etc. to prepare desired grades of alloy in various series like, LM 0 to LM 31 series .The holding furnace tilts gradually to pour the hot, molten Aluminium Metal.
6.) Ingot caster machine:
Different sizes of Ingots or billets can be casted in this process. The metal flows into moulds, the moulds are fitted over a conveyor. As it enters the mould it is cooled by a spraying the fine mist of water on the moulds. As the aluminium cools it hardens and becomes heavier. This makes the base of the mould lower into the pit so that more aluminium flows into the mold. Gradually an ingot is formed.
7.) The ingots:
The ingots are bundled and handled. By an overhead crane They are loaded onto a truck and dispatched to the rolling mill or for further process. The ingots are either used directly in the production of industrial products such as alloy gear boxes and engine blocks (auto components) or converted into aluminium sheets. Sheet aluminium is then used to produce new aluminium cans, house siding, roof, guttering or even aircraft skins.
At the rolling mill the ingots are rolled into a very, very thin sheet which is used by the can making company to make new Beverages drink cans. And the whole process starts all over again!
An over view of aluminum scrap/chip recycling process plant layout by AFECO Industries:
AFECO’s Aluminum Scrap/Chip Recycling Process Plant provides a very efficient and effective technology for scrap/chip recycling with minimum human interference. It is one of the best technology Available in the world for various type of light gauge scrap melting in which the material will be fed into the side well Melting Furnace after shredding DE coating the process. In the side well furnace, liquid molten metal is circulated by the Vortex Pump & a specially designed well cavity. It will have an impact on the metal recovery yield. By pulling dry material subsurface through the vortex, Aluminium metal oxidation is minimized regardless of scrap type.
Hence Recovery rate will be increased and typically 94% max recovery will be received. And the process causes 5% to 6% melt loss, depending on the existing method. If the system is operated properly as per designed layout and controlled Metallurgy process, consistent metal recoveries of 94 %-95% can be expected. And For maximum recovery, salt flux must be required.
Capacity of plant:
Any organization or Promoter person can start a new Business with this “Aluminium Recycling Process Plant” choosing various capacity from 300 kg/hr. to 5000 KG/Hr. Recycling Process.
This plant will be running 24X7 with pre decided output. The Financial Capacity of input material will be the deciding factor for Manufacturing Plant Capacity establishment.
Please click below for the Layout drawing and the Technical specs of the aluminum scrap/chip recycling plant by AFECO Industries:
1)”Chemical Principles, the Quest for Insight, 4th Edition”; Peter Atkins and Loretta Jones; 2008.
2) Waste Online: Metals-Aluminum Recycling.
5) EPA: Aluminum.
Mr. Prakash Radhakrishna Maladkar is a mechanical engineer with around 22 years of experience as a design, manufacturing & marketing professional in the field of “Heating Systems & Equipment” and Foundry Industries & Metallurgy process control. At present, he works as the Managing Director of AFECO HEATING SYSTEMS and visits international and national clients regularly as an Aluminium Chip Processing Plant consultant.