How to recycle waste aluminum alloy?

The pretreatment technology of waste aluminum in China is still very simple and backward. Even in large-scale recycling aluminum plants, there is no advanced technology for the pretreatment of waste aluminum. At present, the following pretreatment technologies are mainly used.

1. Waste aluminum with single variety

The waste aluminum with single variety or basically no other impurities is generally not subject to complex pretreatment, but is stacked separately according to the variety and composition of the waste. When a single type of waste aluminum is used, as long as one component is randomly tested, the batch composition can be known. It is a recycled aluminum raw material. Generally, it can be melted in the furnace without any pretreatment. When smelting a certain type of aluminum alloy, the waste aluminum with corresponding composition and variety can be directly added to the reverberatory furnace for smelting, and it can be easily melted into the corresponding brand aluminum alloy. Some of the waste copper containing high copper and zinc can also be used as master alloys for adjusting the composition of aluminum alloy during smelting. In the enterprises that adopt small reverberatory furnace or crucible furnace, the waste aluminum with large volume shall be broken (cut or other methods) into material fast meeting the furnace specification according to the needs. It is worth mentioning that a small amount of non aluminum metal will be mechanically entrained in some single type of waste aluminum, such as waste steel parts such as screws on waste aluminum doors and windows. Although the content is small, it will seriously affect the quality of the alloy, so it must be separated before smelting.

2. The recycling process of waste aluminum generally goes through the following four basic processes.

(1) Preparation of waste aluminum

First of all, waste aluminum is classified and stacked in different grades, such as pure aluminum, deformed aluminum alloy, cast aluminum alloy, mixture, etc. For the waste aluminum products, they shall be disassembled, the steel and other non-ferrous metal parts connected with the aluminum materials shall be removed, and then the waste aluminum materials shall be made through cleaning, crushing, magnetic separation, drying and other processes. For the light, thin and loose pieces of scrap aluminum, such as the locking arm on the car, the speed gear shaft sleeve and aluminum scraps, they should be packed by hydraulic metal packer. For ACSR, the steel core shall be separated first, and then the aluminum wire shall be wound into coils.

Iron impurities are very harmful to the smelting of waste aluminum. If there is too much iron, brittle metal crystals will be formed in aluminum, which will reduce its mechanical properties and corrosion resistance. The iron content shall be generally controlled below 1.2%. For the scrap lead with iron content more than 1.5%, which can be used as deoxidizer in iron and steel industry, the scrap aluminum with high iron content is seldom used in commercial aluminum alloy smelting. At present, there is no very successful method in aluminum industry to remove the excessive iron in waste aluminum, especially in the form of stainless steel.

Waste aluminum often contains paint, oil, plastic, rubber and other organic non-metallic impurities. Try to remove it before smelting. For the waste aluminum of conductor, mechanical grinding or shear stripping, heating stripping, chemical stripping and other measures can be adopted to remove the coating. At present, domestic enterprises often use high-temperature ablation to remove the insulator, which will produce a lot of harmful gases and pollute the air seriously. If the method of combination of low temperature baking and mechanical stripping is adopted, the insulator will be softened by heat first, the mechanical strength will be reduced, and then it will be peeled off by mechanical rubbing, so that the purpose of purification can be achieved and the insulator material can be recovered at the same time. The coating, greasy dirt and other pollutants on the surface of waste aluminum vessels can be cleaned with acetone and other organic solvents. If they can not be removed, the paint shall be removed by the paint remover. The temperature of the paint remover should not exceed 566 ℃, as long as the waste material stays in the furnace for enough time, the general oil and coating can be removed.

For the aluminum foil paper, it is difficult to separate the aluminum foil layer and the paper fiber layer effectively with the common waste paper pulping equipment. The effective separation method is to heat and pressurize the aluminum foil paper in the aqueous solution first, then quickly discharge it to the low-pressure environment for decompression, and carry out mechanical mixing. This separation method can recover both fiber pulp and aluminum foil.

The liquefying separation of aluminum scrap is the development direction of aluminum recovery in the future. It combines the pretreatment of aluminum scrap with the Remelting Casting, which not only shortens the technological process, but also avoids air pollution, and greatly improves the recovery rate of net metal.

In the device, there is a filter that allows gas particles to pass through. In the liquefying layer, aluminum precipitates at the bottom, and organic matters such as paint attached to waste aluminum decomposes into gas, tar and solid carbon above 450 ℃, and then burns completely through the oxidation device inside the separator. The waste material is stirred by the rotating drum, mixed with the solution in the bin, and the impurities such as sand and stone are separated into the sand and stone separation area. The solution ferry brought out by the waste material is returned to the liquefaction bin through the recycling propeller.

Knowledge of cold working and grinding for recycling waste aluminum alloy

1、 Regeneration and pulverization of waste cans

The flattened and cleaned cans can be directly put into the feed bin, which can be smashed into powder in an instant, with an average particle size of 1-3 mm. The particle size of the products can be adjusted to be basic ball, hemispherical and polygonal. It can be smashed into powder in one time by single machine operation. The process is simple and easy to operate. It covers a small area and has an installed capacity of 15 kW. Each unit is operated by two people and smashes 55-65 kg cans per hour.

2、 Crushing waste aluminum wire, waste cable and bare aluminum wire into powder

For waste aluminum wire, waste cable, single strand or multi strand aluminum wire, first cut the aluminum wire into line segments, according to the requirements of finished powder, cut the length of 4-6 mm.

It is cut into sections by the disc automatic shear. The size of the disc scissors is selected according to the thickness of the smooth aluminum wire and the specifications required by the finished powder. The disc automatic shear cuts 80-120kg of the aluminum line per hour. The larger the diameter, the longer the length and the higher the output of the waste aluminum wire, the 12mm diameter can be cut, the length is not limited, or multiple strands can be cut at the same time, with an installed capacity of 5.5kW.

The raw material of uniform line section is fed automatically and evenly through the blanking port of the crusher, with an hourly output of 30-40 kg, and the installed capacity and product granularity are acceptable.