Four Basic Processes for Recycling Aluminium Scrap The four basic processes for the recycling of scrap aluminum are the following four basic processes for the reprocessing of scrap aluminum.
(1) Preparation of Waste Aluminum Materials
First of all, the primary classification of waste aluminum, graded stacking, such as pure aluminum, deformed aluminum alloy, cast aluminum alloy, 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, hydraulic metal balers are used to press the bags. 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, which contains more than 1.5 % iron, it can be used as a deoxidizer in the iron and steel industry. 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 both 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 maximum 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, general oils and coatings can be removed. 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 the maximum extent, and also makes net metal recovery. The rate has greatly increased.
There is a filter in the device that allows gas particles to pass through. In the liquefaction layer, aluminum precipitates at the bottom, and organic substances such as paints 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 that is not clean, up to 20% of the active ingredients will enter the slag.
(3) Recycled deformed aluminum alloy
Deformed aluminum alloys that can be produced from scrap aluminum alloys include 3003 , 3105 , 3004 , 3005 , 5050, etc., of which mainly 3105 alloys are 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) Recycled Cast Aluminum Alloy
Only a small scrap material is regenerated deformation of aluminum alloy, from about 1/4 then generates a deoxidizer for steel making, and for most of the aluminum alloy casting regeneration. The die-cast aluminum alloys A380 and ADCl0 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 largest 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. In recent years, developed countries have continuously introduced a series of new technological innovations in their production, such as low-cost continuous smelting and processing technologies, which can upgrade low-grade scrap aluminum for manufacturing for casting, die-casting, rolling and Recycled aluminum ingots for master alloys. The largest ingot weight is 13.5t. Among them, the remelted secondary alloy ingot (RSI) can be used to make special plates for cans. The quality of thin plates has reduced the quality of each can to only about 14g ; some recycled aluminum even used For the manufacture of computer floppy disk drive frameworks. In the regeneration process of waste aluminum, the smelting of regenerated aluminum and the treatment of the melt are the key processes to ensure the quality of regenerated aluminum metallurgy. The metamorphism and refining of aluminum melt can not only change the shape of silicon in aluminum-silicon alloys, purify the aluminum melt, but also greatly improve the performance of aluminum alloys. Aluminum melt refining and purification deterioration, the current use of Nacl, NaF, KCI and Na3AIF6 and other chloride salts and fluorine treatment, and some using C12 or C2C16. Processing. The use of chlorine-containing substances for the refining of waste aluminum melts, although effective, may cause serious damage to the human body, the environment, and equipment due to its by-products such as AICI3 , HCl, and Cl . In recent years, people are trying to improve the treatment process and use non-toxic, low-toxic refined metamorphic materials to solve environmental pollution problems, such as the use of N2 , Ar as refining agents, but the effect is not satisfactory. The so-called “pollution-free†refining agents on the market are based on carbonates, nitrates, and a small amount of C2C16 . Since there is still a small amount of nitrogen oxides and chlorine emissions, environmental pollution cannot be completely eliminated. In recent years, newly developed processes for modifying, refining, and refining recycled aluminum with rare earth alloys are expected to completely solve the problem of environmental pollution in the scrap aluminum recovery and smelting industry. The process fully utilizes the interaction characteristics of rare earth elements and aluminum melts, and exerts the function of rarer elements on the refining and metamorphism of aluminum melts, and can realize integrated treatment of purification, refining, and deterioration of aluminum melts, and is not only simple and efficient. , And can effectively improve the quality of recycled aluminum metallurgy. No harmful exhaust gas and other by-products are generated during the entire process.