Meaning
Material balance calculations in secondary smelting use a standard factor to account for the unavoidable destruction of metal during heating. The melt loss allowance represents the agreed-upon percentage of raw material weight lost to dross during the melting process. This factor determines the net weight of usable metal returned to the scrap owner.
Yield Calculation
Calculating the metal balance requires comparing the dry weight of incoming scrap against the weight of the recovered ingot. The melt loss allowance is deducted from the received weight to establish the baseline for the expected yield. Clean ingots require a minimal deduction, whereas thin foils and turned chips demand a much higher factor due to their large surface area.
This baseline deduction protects the furnace operator from bearing the financial cost of unavoidable dross generation.
Contract Negotiation
Establishing these limits in tolling agreements requires a detailed understanding of the material’s history and contamination levels. Negotiating the melt loss allowance involves balancing the furnace performance data against the supplier’s expectations of metal recovery. When the scrap contains heavy coatings of paint or oil, the allowance must be increased to cover the non-metallic fraction that will burn away during processing.
This agreement ensures that both parties share the financial risk of material impurities.
Recovery Control
Reducing actual furnace losses below the contracted limit allows the processor to retain the excess metal as a bonus margin. Monitoring the melt loss allowance against actual recovery values helps identify when burner settings or fluxing procedures need adjustment. When the actual loss exceeds the allowance, the processor must absorb the cost of the missing metal, which incentivizes continuous improvement in furnace operation.
This ongoing tracking of melt efficiency helps the engineering team maintain optimal combustion and skim removal practices.
