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Situation
Drosses, containing up to 70 or 80% by weight of aluminium, are always generated whenever molten aluminium is produced in furnaces.
Problem
Drosses oxidise readily above 400°C, causing a loss of valuable aluminium metal. The dross needs to be cooled as rapidly as possible, safely and cheaply. Air cooling means losing valuable aluminium metal. Other mechanical methods use moving parts which are expensive to maintain and unreliable and cannot cool all types of drosses under all conditions.
Solution
The IGDC system, designed and commercialised by STAS, consists of a compartmentalised skim pan placed in a sealed hood, with a low flow of inert gas to prevent oxidation. There are no moving parts, no generation of dust and no cooling water; as a result, aluminium recovery in a separate operation is optimised. There are virtually no maintenance costs, and environmental and working conditions are improved.
Advantages
- Low operating, maintenance and capital costs.
- No water used for cooling: safe process.
- Improves environmental and working conditions.
- Individual units permit maximum flexibility in sizing of capacity needs.
- Treats all drosses, particularly highly reactive drosses.
- No baghouse required.
- Increases recovery of aluminium due to the inert gas.
- Modular and individual units, available in different sizes.
- No infrastructure required.
- Dross temperature at beginning: 700 to 780°C
- Dross temperature at the end: less than 400°C
- Cooling cycle: about 6 hours
- Aluminium recovered: maximum (no oxidation)
Dimensions and Weight of a Typical Dross Cooler:
- Cooler: 3.6m x 2.3m x 3.3m H, 2100 kg
- Dross pan: 2750 kg
- Single cast ductile iron pan
- Sized from 0.47 to 0.95 m2
- Capacity determined by dross density which ranges from 900 to 1600 kg/m3
Gas Flow Rate:
- Argon or nitrogen: Pressure: 413 kPa (60 psi)
Flow: 280 slpm to fill-up, then 11 slpm for balance of cycle
Power Requirements:
- 500 VA, 220 to 600 VAC, 1 or 3 phases, 50 or 60 Hz
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Accessories and Consumables |
- Cooling cycle control based either on timer or temperature of dross pan (not both).
- Relay and time-relay based logic.
- Standard system controls two IGDCs.
- Stainless steel enclosure.
- Control panel controlled with PLC:
- Optimized cooling by combining time and temperature control.
- Dumper:
- Adapted to a forklift, the pan can be transported and emptied in its designated place or into a container by a mechanical system that completely overturns the pan utilizing gravity.
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