[China Aluminum Industry Network] Do you know what aluminum scrap is made of?
1. Guangzhou Scrap Recycling: Aluminum scrap often contains non-metallic impurities like paint, oil, plastic, and rubber. Before it can be smelted, these materials must be removed as much as possible. For wire-type aluminum scrap, methods such as mechanical abrasion, shear stripping, heat treatment, or chemical cleaning are commonly used to remove the insulation layer. In China, many companies use high-temperature ablation techniques, which, while effective, release large amounts of harmful gases, causing serious air pollution.
2. A more environmentally friendly alternative involves low-temperature baking followed by mechanical peeling. This process first softens the insulator using heat, reducing its mechanical strength, making it easier to remove through rubbing. Surface contaminants like coatings and oil on aluminum waste containers can be cleaned with solvents like acetone. If this isn't sufficient, paint-stripping ovens can be used, with temperatures not exceeding 566°C. As long as the material stays in the oven for a sufficient time, most oil and paint can be effectively removed.
3. Iron impurities are a major concern during the smelting of aluminum scrap. Excessive iron can lead to brittle metal crystals, reducing the mechanical strength and corrosion resistance of the final product. The iron content should generally be kept below 1.2%. If the iron content exceeds 1.5%, the scrap may be used as a deoxidizer in the steel industry, but it's rarely used in commercial aluminum alloy production. Currently, there’s no widely accepted method in the aluminum industry to effectively remove excess iron, especially when it comes in the form of stainless steel.
4. For aluminum foil recycling, traditional paper pulping equipment struggles to separate the aluminum layer from the paper fibers. An efficient method involves heating the aluminum foil in an aqueous solution under pressure, then rapidly releasing it into a low-pressure environment. This causes the material to decompress and allows mechanical stirring to separate the layers, recovering both the fiber pulp and the aluminum foil.
5. The liquefaction and separation of waste aluminum is becoming a key trend in future aluminum recovery. This method integrates the pretreatment of aluminum waste with re-melting, streamlining the process, reducing environmental impact, and significantly improving the recovery rate of valuable metals.
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