Hydro Aluminium in Commerce, TX, placed an order for the supply of a modern batch homogenizing furnace for extrusion billet from with Hertwich Engineering, a company of the SMS group. Hydro already operates a continuous homogenizing furnace (also from Hertwich) at the Commerce site, where the company processes some 100,000 tonnes of aluminium scrap into extrusion billets annually.
The new batch homogenizing furnace will have a capacity of 55 tonnes and is designed for billets up to a maximum length of 7.7 m and diameters in the range 178-406 mm. It is a modernized concept for extrusion billet homogenization developed by Hertwich in 2010. The design includes a new heating system and automated log handling that makes it comparable to a continuous homogenizing furnace. The decisive advantage of the design is the heating.
With conventional batch furnaces, the air releases thermal energy when passing through the material being heated. This leads to non-uniform temperature distribution. Longer heating times are necessary to compensate for the temperature differences. The concept of the new batch furnace combats this disadvantage by changing the direction of air flow within the furnace (using so-called reversed air). Thus, billets in the furnace are heated more uniformly and heating time can be reduced.
The air flow direction is reversed with the help of flaps. The fan operates at full power during flow reversal. The energy supplied via the fan suffices to balance out the heat loss during the soaking time. No external heating (whether supplied via burners or electrically) is necessary during this period. During operation, the temperature is kept constant using frequency-controlled fans. Baffles enable the hot gases to be distributed uniformly throughout the whole furnace chamber. The chamber is designed in such a way that uniform air flow is not impeded or prevented anywhere in the chamber.
Cooling is carried out in a similar manner to heating. The the reversible air flow ensures that the temperature is uniform during cooling, with correspondingly better metallurgical results.
Hydro will arrange its two homogenizing furnaces at Commerce in such a way that they can operate in combination, enabling flexibility in carrying out the homogenization process. In addition, the Commerce facility is installing a second sawing plant to eliminate waiting times. A transfer car coupled with an automated stacker and spacer handling will be used to transport the billets.