Nov 23 2006
An idea and some stubborn engineers was all it took. Hydro's aluminium casthouse in Neuss has closed the metal loop and strengthened its relationship with the nearby rolling mills in Neuss and Grevenbroich.
Hydro’s metal plant Rheinwerk Neuss now annually remelts 22,000 tonnes of foil scrap from the Grevenbroich rolling mill.
“This pays an environmental benefit and improves our competitive position, when you consider the high electricity prices,” says plant manager Berhard Eich.
Each year, Hydro produces 224,000 tonnes of primary aluminium at Neuss, which is Germany’s largest electrolysis plant. The Neuss casthouse delivers 320,000 tonnes of rolled products ingot annually to Alunorf, which in turn delivers aluminium coil to Hydro’s foil mill at Grevenbroich.
Usually the plant must buy the surplus volume as costly cold metal. To save costs, a team of engineers led by project manager Michael Jordan has work day and night to find a solution to utilize the valuable production scrap from the Grevenbroich rolling mill. Until now, the foil from Grevenbroich – just 6 micrometers thick – could only be remelted for reuse in the packaging industry.
The problem is that the thin foil is covered by a thin oxide layer that works as insulation. In addition, the compressed foil has a density significantly lower than liquid aluminium. This caused scrap foil to float on top of the liquid metal, causing a lot of dross formation. The thin foil burned instead of melting.
The engineers at Neuss wondered how they could make better remelting conditions and came up with the idea to introduce an electromagnetic pump that would circulate liquid metal at high speed. The circulating metal would form a whirlpool inside the pump, which is called a Vortex pump.
When compressed foil in bricks measuring 40 x 40 cm is added through a funnel, the gravity force forces the scrapped foil into the whirlpool and below the metal surface where the turbulence current is formed. The circulating metal then erodes the scrapped, thin foil, and the foil scrap is remelted perfectly.