I have a furnace for aluminum recycling wherein dross formation is a major issue. It reduces the yield by about 10-12%.

I am looking for a change in process parameters or other solutions through which I can reduce the dross formation.


1 Answer 1


The dross is mostly composed of aluminium oxide which is already present on the surface of the metal before it even goes into the furnace, as the aluminium melts the oxides separate and float to the top.

Recycled aluminium will tend to be made up of relatively thin material with a high surface area to volume ratio and so a relatively high proportion of surface oxide compared to ingots, especially if the material has been anodised.

For example if the oxide layer is 4 micrometers thick then on a 5kg ingot this is a negligible amount but if you are melting 0.1mm thick foil then a the oxide layer on both sides is getting on for 10% of the total thickness.

So a lot of the dross is simply separating out what is already present in the starting material which you can do very little about .

You can minimise any additional oxide formation during melting by controlling the atmosphere in the furnace to reduce oxygen availability although how practical this is depends on the setup being operated.

Separating the material by thickness and adding the thinner stuff to already molten metal would also help a bit.


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