ã€China Aluminum Industry Network】 The recycling of scrap aluminum is generally done through the following four basic processes.
(1) Preparation of waste aluminum materials First, the primary classification of waste aluminum is carried out, and it is stacked in layers, such as pure aluminum, deformed aluminum alloys, cast aluminum alloys, and mixed materials. For waste aluminum products, dismantling shall be carried out, steel and other non-ferrous metal parts connected with aluminum materials shall be removed, and waste aluminum materials shall be prepared through the processes of cleaning, crushing, magnetic separation and drying. For thin, loose and flaked aluminum parts, such as locking arms, speed gear bushings, and aluminum shavings on automobiles, use a hydraulic metal baler to compress the bag. For ACSR, the steel core should be separated and then the aluminum wire wound into a roll.
Iron impurities are very harmful to the smelting of aluminum scrap. When the iron is too much, brittle metal crystals are formed in the aluminum, thereby reducing its mechanical properties and weakening its corrosion resistance. Iron content should generally be controlled below 1.2%. For lead with an iron content of 1.5% or more, it can be used as a deoxidizer in the iron and steel industry, and commercial aluminum alloys are rarely used for smelting scrap aluminum with high iron content. At present, there is no successful method in the aluminum industry to satisfactorily remove excess iron in scrap aluminum, especially in the form of stainless steel.
Waste aluminum often contains organic non-metallic impurities such as paints, oils, plastics, and rubber. Before smelting, you must try to remove it. For wire type scrap aluminum, mechanical abrasion or shear stripping, heat stripping, and chemical stripping can be used to remove the wrapper. At present, domestic companies commonly use high-temperature ablation methods to remove insulators, and a large amount of harmful gases will be generated during the ablation process, which will seriously pollute the air. If the combination of low-temperature baking and mechanical peeling is used, the insulator is first softened by heat, the mechanical strength is reduced, and then it is peeled off by mechanical rubbing so that the purpose of purification can be achieved and the insulator material can be recovered. The coating, oil, and other contaminants on the surface of aluminum waste containers can be cleaned with acetone and other organic solvents. If they cannot be removed, paint stripping ovens should be used for paint stripping. The higher temperature of the stripping furnace should not exceed 566 °C. As long as the waste material stays in the furnace for a sufficient period of time, the general oil and coating can be cleaned.
For aluminum foil paper, it is difficult to separate the aluminum foil layer and the paper fiber layer effectively by ordinary waste paper pulping equipment. An effective separation method is to first heat aluminum foil in an aqueous solution, pressurize it, and then quickly discharge it to a low-pressure environment. , And mechanical stirring. This separation method can recover both fiber pulp and aluminum foil.
The liquefaction and separation of aluminum scrap is the development direction of metal aluminum recovery in the future. It combines the pretreatment of aluminum scrap with remelting, which not only shortens the process flow, but also avoids air pollution to a greater extent, but also makes the net metal The recovery rate has greatly increased.
The device has a filter that allows gas particles to pass through. In the liquefaction layer, aluminum precipitates at the bottom, organic substances such as paint attached to the scrap aluminum decompose at 450°C into gas, tar, and solid char, and then pass through the oxidizer inside the separator. Completely burned. The waste is stirred by a rotating drum, mixed with the dissolving liquid in the bunker, and impurities such as sand and gravel are separated into the gravel separation area. The dissolved fertilization brought out by the waste is returned to the liquefaction tank through the recovery propeller.
(2) Ingredients According to the preparation and quality conditions of waste aluminum materials, according to the technical requirements of recycled products, choose and match and calculate the amount of various materials. Ingredients should consider the degree of oxidation of the metal burned, silicon, magnesium oxide burning than other alloying elements to large, the burning rate of various alloying elements should be determined in advance through experiments. The physical specifications and surface cleanliness of waste aluminum materials will directly affect the quality of recycled products and the metal yield. With the exception of waste aluminum, which is not clean, there will be 20% of active ingredients entering the slag.
(3) Recycled Deformation Aluminium alloys used for scrap aluminum alloys can be produced from deformed aluminum alloys of 3003, 3105, 3004, 3005, 5050, etc., of which 3105 alloys are mainly produced. In order to ensure that the chemical composition of the alloy material meets the technical requirements and the pressure processing process needs, a part of the original aluminum ingot should be added when necessary.
(4) The process flow of reclaimed casting aluminum alloy is shown in Figure 1-19. Only a small part of the waste aluminum material is regenerated into deformed aluminum alloy, about 1/4 of which is regenerated into a deoxidizer for steelmaking, and most of it is used for reclaiming aluminum alloys for casting. The die-cast aluminum alloys A380, ADC10, etc. that are widely used in the United States, Japan, and other countries are basically recycled with scrap aluminum.
The main equipments for reclaimed aluminum are smelting furnaces and refining and purifying furnaces, and generally use dedicated static furnaces for fuel or gas. China's larger reclaimed aluminum company is Shanghai Xinge Nonferrous Metals Co., Ltd., located in the suburbs of Shanghai. The company has two 50-ton smelting and standing furnaces, a group of 40-ton fuel smelting and standing furnaces, and a 12-ton fuel rotary kiln. Small enterprises can use kiln such as tank kiln and kiln.
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