WITH OF WITHOUT SALT : The Great Debate
In principle a TRF does not require salt to melt the whole range of aluminium scrap.
With a slight over-pressure and a correctly adjusted burner the TRF offers the same yields as a fixed axis rotary operating using large amounts of salt.
In reverb type furnaces with or without side wells scrap is melted without salt.
A TRF is in fact a rotating reverb chamber operating without parasite air in which you can melt just about anything. This is not the case for a fixed reverb in which you cannot melt dross, irony-cast, swarf or shredded scrap
Why use salt in a TRF ?
If, theoretically, no salt is required in the melting process, it is advisable to use a small quantity (7 – 10% of the charge for highly oxidized scrap and 3 – 4% for non-oxidized scrap) to promote cleaning once the metal has been cast.
If salt is not used cleaning the chamber can take up-to 50 – 60 minutes whereas with salt cleaning can take as little as 10 minutes.
In a fixed axis rotary the quantity of salt should equal the weight of oxides + 10%.
For example: 100 kg of dross – 50 % Aluminium/50% oxides + 10 % = 55 kg of salt. However in a TRF only 10 kg is necessary.
Salt slows the exothermic reaction, improves casting conditions and keeps the refractory clean.
The disadvantage is the creation of salt polluted ash.
Without salt, particular attention should be paid to the melt cycle, furnace temeperature and strict adherence to melt times in order to avoid creating an exothermic reaction and loosing metal.
However, ash build-up on the walls will be greater and cleaning time much longer. But residual ash will be free from salt and reusable in the cement industry.
At the end of the day the decision is an economical one, the only certitude is that the TRF is presently the best furnace on the market,
Energy consumption : Lowest
Production : Highest
Metal Yields : Greatest
TRF designed & built by Dross Engineering have a number of patented technical advantages:
* Heating equipment and combustion management :VARI- GAS
* Rotary drive : ROTAX
* Automated compensation for thermal expansion/contraction
* Automated rear-tap casting