Implementation of Metal Casting Best Practices - EERE - U.S. ...

lost mainly through the hot flue gases. In addition, as the molten metal contacts the furnace gases
it forms slag/dross resulting in a melt loss rate of 3% to 5% in aluminum. 47
The assessment team recommended that the plant perform a study to ascertain the costs and
benefits of replacing their reverberatory furnaces with stack melters. Although this is very
capital-intensive proposition, the assessment team felt that over time stack melters could provide
significant cost reductions, especially if natural gas prices remain high.
A stack melter can be considered a modified reverberatory furnace wherein better furnace
sealing and the use of flue gases to preheat the charge materials improves efficiency. The hot
exhaust gases from the melting zone flow through the shaft to preheat the incoming charge, thus
resulting in an energy efficiency of 40 to 50%, 48 which is a significant improvement over the 20
to 25% efficiency of the reverberatory furnaces currently installed at this facility.
3. Conclusion
This facility has utilized NADCA/government-sponsored research results to make significant
improvements in its operation, especially in the area of die life. Implementation of other energysaving
practices, as identified by the BestPractices program and furnace/molten metal practices
research, can also add to the facility’s profitability without requiring significant capital
investments. Installing more efficient melting equipment such as stack melters, although capital
intensive, will add significant savings over time and is worth consideration to estimate benefits
and payback period.
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