Four Basic Processes for Recycling and Processing of Waste Aluminum

West Aluminum - West Aluminum Industry Telecom:Today, let's know how to process scrap aluminium in the industry. Recycling of scrap aluminium usually goes through the following four basic processes.

1. Preparation of scrap aluminium

Firstly, scrap aluminium is classified and stacked in different grades, such as pure aluminium, deformed aluminium alloy, cast aluminium alloy and mixtures. For scrap aluminium products, the scrap aluminium products should be disassembled, the steel and other non-ferrous metal parts connected with aluminium materials should be removed, and then the scrap aluminium products should be made by cleaning, crushing, magnetic separation, drying and other processes. For light and loose pieces of scrap aluminium, such as locking arm, speed gear sleeve and aluminium scraps on automobiles, it is necessary to press them into packages by hydraulic metal baler. For steel-cored aluminium strands, the steel cores should be separated first, and then the aluminium wires should be wound into coils. Iron impurities are very harmful to the smelting of scrap aluminium. Brittle metal crystals will be formed in aluminium when iron is excessive, which will reduce its mechanical properties and reduce its corrosion resistance. Iron content should generally be controlled below 1.2%. For waste lead containing more than 1.5% iron, it can be used as deoxidizer in iron and steel industry. Commercial aluminium alloys seldom use waste aluminium with high iron content for smelting.

At present, there is no very successful method in the aluminium industry to remove excess iron from scrap aluminium satisfactorily, especially iron in the form of stainless steel. Waste aluminium often contains organic non-metallic impurities such as paint, oil, plastics, rubber and so on. It must be removed before refining. For wire scrap aluminium, mechanical grinding or shear peeling, heating peeling, chemical peeling and other measures can be used to remove the wrapping. At present, domestic enterprises often use high temperature ablation to remove insulators, which will produce a large number of harmful gases and seriously pollute the air. If the method of combining low temperature baking with mechanical peeling is adopted, the insulator will be softened by heat energy, and the mechanical strength will be reduced. Then the insulator will be peeled off by mechanical kneading, so that the purpose of purification can be achieved and the insulator material can be recovered at the same time.

Coatings, oil stains and other contaminants on the surface of waste aluminium utensils can be cleaned by organic solvents such as acetone. If they can not be cleaned up, paint removal furnace should be used. The higher temperature of the paint remover should not exceed 566 C. As long as the waste material stays in the furnace for enough time, the general oils and coatings can be cleaned up. For aluminium foil paper, it is difficult to separate the aluminium foil layer from the paper fiber layer effectively by using ordinary waste paper pulping equipment. The effective separation method is to heat and pressurize the aluminium foil paper in aqueous solution first, then quickly discharge it to the low pressure environment for decompression and mechanical stirring. This separation method can recover both fibre pulp and aluminium foil.

The liquefaction separation of scrap aluminium is the development direction of recovering metal aluminium in the future. It combines the pretreatment of scrap aluminium impurities with remelting and casting, which not only shortens the process flow, but also avoids air pollution to a great extent, and greatly improves the recovery rate of net metal. In the waste aluminium liquefaction separation device, there is a filter that allows gas particles to pass through. In the liquefaction layer, aluminium precipitates at the bottom. Organic substances such as paint adhered to the waste aluminium are decomposed into gas, tar and solid carbon at 450 ~C, and then burned completely through the oxidation device inside the separator. The waste is agitated by a rotating drum, mixed with the solution in the silo, and impurities such as sand and gravel are separated into the sand and gravel separation zone. The dissolution of the waste is carried out and returned to the liquefaction silo by recycling the propeller.

2. Ingredients

According to the preparation and quality of aluminium scrap and the technical requirements of recycled products, the amount of various materials is selected and calculated. The burning rate of silicon and magnesium is larger than that of other alloying elements. The burning rate of various alloying elements should be determined by experiments in advance. The physical specifications and surface cleanliness of aluminium scrap will directly affect the quality of the recycled products and the metal yield. In addition, 20% of the effective ingredients will enter the slag when the oil is removed from the scrap aluminium.

3. Recycled Deformed Aluminum Alloy

There are 3003, 3105, 3004, 3005, 5050 wrought aluminium alloys which can be produced by scrap aluminium alloys, among which 3105 alloy is mainly produced. In order to ensure that the chemical composition of the alloy meets the technical requirements and the technological requirements of pressure processing, some primary aluminum ingots should be added when necessary.

4. Recycled Cast Aluminum Alloy

Only a small part of waste aluminium is regenerated into deformed aluminium alloy, about 1/4 of which is regenerated into deoxidizer for steelmaking, and most of which are used for regenerated aluminium alloy for casting. Die-casting aluminium alloys A380 and adcl0 widely used in the United States, Japan and other countries are basically recycled from scrap aluminium. The main equipment of reclaimed aluminium is smelting furnace and refining purifying furnace. Generally, the special static furnace for fuel or gas is used.

(Chongqing Xialu Xinda Aluminum Industry Co., Ltd. Publicity Department collates contributions)

Source: Network

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