Although the production of aluminium requires a great deal of energy, the material is very easy to recycle: once it has been produced, it can be reprocessed as often as required to maintain the same quality. Processing plants, for example in rim production, where up to 60 tonnes of aluminium chips are produced per day, therefore collect the material for reuse and melt it down. If this is done on site and without a detour via a melting shop, a conventional furnace is usually used. This results in considerable burn-up, i.e. material loss through incineration and slagging – approximately three to five percent of the aluminium to be recycled is lost.
Three factors can be used to positively influence the amount of burn-up and energy consumption during the melting process: The aluminium chips must be free of oil residues, they must be heated before being fed into the melting chamber and they must mix with the liquid metal as quickly as possible. ARP’s systems take advantage of all these factors – for example, burn-up losses are reduced from up to five to less than one percent and energy consumption is halved.
The “ARP Cyclone Technology” starts with the acceleration of the mixing of liquid metal and chips. The principle of the centrifugal separator for separating solid particles from flows is reversed here and used to guide the chips more quickly under the surface of the molten metal bath. This is because if the aluminium particles remain on the surface for only a few seconds, excessive oxide and slag formation occurs. The liquid aluminium is set in motion at one point in the melting furnace and forms a vortex or cyclone. The cleaned, hot chips are then fed into this vortex in a controlled manner and melted by the liquid medium.
Three per cent less burn-off corresponds to 30 kilograms of additional yield when recycling one tonne of aluminium. With a plant capacity of 24 tonnes per day and an annual operating time of 330 days, this results in approximately 230 tonnes more aluminium per year. In addition, the amount of energy required for melting down is reduced from 1,500 kilowatt hours per tonne to around 800 kilowatt hours per tonne because the waste heat from the thermal post-combustion of the melting furnace waste gas is used to heat the chips via a heat exchanger, the distance between the heat exchanger and the furnace is very short and the system is closed – which means that hardly any heat is lost. The reduction of the energy demand corresponds to a CO2 saving of about 1 clomid tablet 50mg.129 tons per year and system.
“It was important for us to look at the entire process and not just turn a single screw with the improvements”, explains Wolfgang Riegert, managing partner at ARP GmbH & Co. KG. “The previous systems did not work together, and there are practically no full-range suppliers in this field.” The opinion that one should save on aluminium foil or beverage cans is widespread, but Wolfgang Riegert is certain: “With the savings we have been able to make in material and energy use, aluminium will certainly soon get rid of its bad reputation”.