The TRF furnace (tilting rotary furnace) used to melt aluminum scrap has demonstrated for more than 20 years that it is the best furnace for melting aluminum waste (cans - rolled profiles - paper - chips and dross )
It also demonstrated that it had the best thermal efficiency, but also an inconvenience the need for a little salt 7/10%
TRF can, if used properly, melt aluminum without salt, but in reality the furnace door is often open too long when the metal is poured and the ashes come out.
Its open door phases let in a lot of air which triggers an exothermic reaction in the furnace with the air the aluminum oxides burn rising the temperature of the furnace is over 1200°C
This temperature turns the ashes sticky and clogs the walls of the furnace making it difficult to clean
This rise in temperature melts the free iron which is in the ashes. Its melting degrades the quality of the molten alloy
The use of 7/10% salt avoids the adhesion of dirt to the wall and facilitates its cleaning and it is only used for this
7/10% of salt in the load of the furnace is not a lot but this salt requires treating the dross and its financial cost is not negligible
What we have modified on our Patent FR 2 844 345 A1
1/To avoid the exothermic reaction by limiting air inlets, we have developed a new door for our TRFs which accompanies the movement of the shell and releases the furnace inlet by a movement perpendicular to the furnace shell (deformable parallelogram)
2/ To limit the loss of metal locked up in the ashes, we have reversed the exit of the liquid metal because on the current TRF furnace the metal exits the furnace with the ashes by tilting
A small amount of aluminum remains trapped in the ashes and burns during the thermal reaction (loss of metal)
to avoid this problem we thought of pouring the metal by gravity without tilting the furnace, for this, we designed a gravity casting block with a removable cone placed at the back of the shell the metal at the end of the fusion is concentrated at the bottom under the ashes protected from the air, it is cast with the door closed (no air inlet)
During the casting of the metal the burner is stopped to lower the temperature of the ashes and the refractory lining
After the casting of the metal the door is partially opened the shell is rotated to empty the ashes
Limitation of door opening minimizes the entry of air and also prevents the start of an exothermic reaction the dry ashes are easily emptied into the bins
Results :
Improved metal yield
The ashes no longer contain liquid metal or very little
Metal not enriches with iron
Recyclable ash (oxides) without salt can be recycled in cement plant
Or make aluminates that can be used in the steelworks
To distinguish our new TRF we have taken a free name used the last century
To designate the converters of the “KALDO” era
March 2022

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