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.
A method for removal of organic coatings from loose aluminum scrap includes passing the scrap through a Multiple Hearth Furnace operatively maintained in the range of 500° F.-1600° F. Each hearth in the furnace is independently temperature controlled and held under a slightly negative pressure environment. The hearths heat the scrap such that pyrolysis of the coatings occurs within the hearth. Organic compounds liberated during this process are partially or entirely consumed within the furnace combustion products are exhausted through the top. Hydrogen fluoride contained in the products of combustion is incinerated prior to final discharge from the system and routing to additional environmental equipment for particle removal. Scrap is continuously fed into the top of the furnace, and agitated and mechanically moved within each hearth toward an output of another hearth therebelow. The agitation and movement of the scrap exposes the scrap to the hearth atmosphere to assist in processing of the scrap. The discharge of the scrap in the final hearth supplies hot (250° F.-900° F.), clean material for the next step in the process for secondary aluminum recycling.
