[China Aluminum Industry Network] The recycling of scrap aluminum is usually performed through the following four basic processes.
(1) Preparation of waste aluminum materials First, the primary classification of waste aluminum, graded accumulation, such as pure aluminum, deformed aluminum alloy, forged aluminum alloy, mixed materials and so on. With regard to waste aluminum products, dismantling shall be carried out, steel and other non-ferrous metal parts connected with the aluminum materials shall be removed, and the waste aluminum materials shall be made through the processes of cleaning, crushing, magnetic separation, and drying. With regard to frivolous and loose aluminum scrap parts, such as locking arms, speed gear bushings, and aluminum shavings on automobiles, hydraulic metal balers are used to compress bags. Regarding ACSR, you should first separate the steel core and then wind the aluminum wire into a roll.
Iron impurities are very harmful to the exercise of aluminum scrap. When the iron is too much, it will constitute a brittle metal crystal in aluminum, and then reduce its mechanical function and weaken its anti-corrosion ability. Iron content should normally be controlled below 1.2%. With regard to lead scrap containing more than 1.5% iron, it can be used as a deoxidizer for the iron and steel industry. Commercial aluminum alloys are rarely used for smelting aluminum scrap with high iron content. At present, there is no successful way in the aluminum industry to satisfactorily remove excess iron in scrap aluminum, especially in the form of stainless steel.
Aluminum waste is often rich in organic non-metallic impurities such as paints, oils, plastics, and rubber. Before resuming work, we must try to eradicate it. With regard to aluminum scraps of the wire type, it is usually possible to remove the wrapping by mechanical grinding or shearing, heat stripping, chemical stripping, and the like. At present, domestic companies commonly use high-temperature ablation methods to remove insulators, and a large amount of harmful gases will occur during the ablation process, which will seriously pollute the air. If the combination of low-temperature baking and mechanical peeling is selected, the insulator is first softened by the heat energy, the mechanical strength is reduced, and then it is peeled off by mechanical tamping. This can not only reach the purifying intention, but also can recover the insulator data. The coating, oil, and other contaminants on the surface of the waste aluminum containers can be cleaned with organic solvents such as acetone. If they cannot be removed, the paint stripping furnace should be used for paint stripping. The higher temperature of the paint stripping furnace should not exceed 566 °C. Only when the waste material stays in the furnace for enough time, the oil and coating can be removed.
With respect to aluminum foil paper, it is difficult to separate the aluminum foil layer from the paper fiber layer with ordinary waste paper pulping equipment. A useful method of separation is to place the aluminum foil paper in an aqueous solution for heating, pressurization, and then quickly discharge it to a low-pressure environment. , And mechanical mixing. This method of separation can not only recover fiber pulp but also recover aluminum foil.
The liquefaction of aluminum scrap is the development direction of recovering aluminum metal in the future. It combines the pre-disposal of scrap aluminum mixed with re-melting, which not only shortens the technical process, but also prevents air pollution at a greater limit, and makes the net metal The recovery rate has greatly increased.
There is a filter in the equipment that allows gas particles to pass through. In the liquefaction layer, aluminum precipitates at the bottom, and organic substances such as paint attached to the scrap aluminum decompose into gas, tar, and solid carbon at temperatures above 450°C, and then pass through the oxidation equipment inside the separator. Burn it thoroughly. The waste is mixed with a rotating drum and mixed with the dissolving liquid in the bin. The impurities such as sand and gravel are separated from the separated area of ​​the gravel. The dissolved fertilization brought out by the scrap 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, the deployment and calculation of the amount of various materials are selected. Ingredients should consider the degree of metal oxide burning, silicon, magnesium oxide burning than other alloying elements to large, the burning rate of various alloying elements should be determined in advance by testing. The physical standards and apparent 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, it will have 20% of the useful components entering the slag.
(3) Regeneration Deformation Aluminium alloys produced from scrap aluminum alloys can be produced in 3003, 3105, 3004, 3005, 5050, among which the first is the production of 3105 alloy. In order to ensure that the chemical composition of the alloy data meets the technical requirements and technical requirements for pressure processing, a part of the raw aluminum ingot should be added as necessary.
(4) As long as a small part of the recycled aluminum alloy aluminum scrap material is regenerated into deformed aluminum alloy, approximately 1/4 of the aluminum alloy scrap material is regenerated into a deoxidizer for steelmaking, and most of the material is used for regenerating aluminum alloy forging. 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 primary equipment for reclaimed aluminum is smelting furnaces and refined purification furnaces. A dedicated stationary furnace for fuel oil or gas is usually used. China's larger reclaimed aluminum company is located in the Shanghai suburb of Shanghai Newcastle Nonferrous Metals Co., Ltd., the company has two sets of 50t smelting static furnace, a set of 40t fuel smelting static furnace; a 12t fuel rotary kiln. Small companies can choose to use pool kiln, kiln and other exercises.
During these years, developed countries have continuously introduced a series of new skills innovations in production, such as low-cost successive smelting and disposal technologies, which can enable low-grade scrap aluminum to be upgraded for use in forging, die-casting, rolling and Recycled aluminum ingots for master alloys. Larger ingots weigh 13.5 tons, during which remelted secondary alloy ingots (RSI) can be used to make special plates for cans. The quality of thin plates has reduced the quality of each can to about 14 g; some recycled aluminum, even The structure used to make a computer floppy disk drive.
In the regeneration process of aluminum scrap, the smelting of regenerated aluminum and the disposal of the melt are the critical processes for ensuring the quality of the regenerated aluminum metallurgy. The transformation and refinement of the aluminum melt not only can modify the morphology of the silicon in the aluminum-silicon alloy, it can purify the aluminum melt, and can greatly improve the function of the aluminum alloy. The essence of aluminum melt transformation and purification, the current selection of Nacl, NaF, KCI and Na3AIF6 and other chlorine salts and fluoride salts disposal, and some use C12 or C2C16 for disposal.
The use of chlorine-containing substances in the essence of waste aluminum melt, although the role is good, but its byproducts AICI3, HCl and Cl, etc. will cause serious harm to the human body, the environment and equipment. Over the years, we are striving to improve our disposal techniques and use non-poisonous, low-toxicity materials to solve environmental pollution problems. For example, N2, Ar, etc. are used as a refinement, but the effect is not perfect. The so-called “pollution-free†essence is commercially available, whose basic components are carbonates, nitrates, and a small amount of C2C16. Since there are still a few nitrogen oxides and chlorine gases emitted, the environmental pollution cannot be completely eliminated.
In recent years, newly developed technologies for the transformation, refinement, and refinement of recycled aluminum with rare earth alloys are expected to completely solve the problem of environmental pollution caused by the recycling of scrap aluminum. This technology makes full use of the interaction between rare earth elements and aluminum melts, and represents the refinement and transformation of rare earth elements on aluminum melts. It can complete the integrated purification, refining, and transformation of aluminum melts. It is not only concise and efficient. , And can usefully improve the metallurgy quality of recycled aluminum. Harmful exhaust gas and other by-products will not occur throughout the disposal.
Responsibility editor: mm
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