De-coating Unit For Aluminium Scrap

The de-coating is a thermal treatment applied on the aluminium scrap, used to remove from the surface of the material all the contaminants as paper, oil, links, paint, plastic.

The aluminium scrap is used as “raw material” to produce new aluminium but before to be molten again has to be “cleaned”, meaning treated inside a de-coating unit, in order to reach the specific characteristics requested. If the scrap is not cleaned (de-coated), and is molten directly inside the furnace, the metal loss increase and the presence of contaminants in the furnace create many problems to the use of the regenerative burners and produce an additional cost of the natural gas used in the melting.

Moreover the combustion of pollutants in the post-combustion chamber, allows a best oxidation of the pollutants due to the oxidation temperature over 850 °C, a residence time over 2 seconds and a oxygen content over 6%. The final treatment with fabric filter and dosage of bicarbonate and activated carbon, complete the treatment with the removal of contaminants that cannot be oxidised.

The scraps to be cleaned are introduced inside the rotary kiln and is heated by means of hot gas in a controlled atmosphere. The high temperature of the gas provide to melt and produce the gasification of the organic material, removing it from the aluminium scrap.

To avoid oxidation of the aluminium scraps, to produce scales and to lose the control of process temperature due to auto-combustion, the heating of scraps must be carried out by means of flue gas poor of oxygen, as with the “Pyrolysis” process.

The experience on existing pyrolysis plants, allow to cover the following scraps: turning, cover, ground, cans, tubes or caps, cables, sheets laminated with paper or plastic, sheets coated.

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