Meaning
Metallurgical measurements of metallic oxidation during melting determine the net weight of usable alloy recovered from a furnace charge. A dross loss calculation accounts for the difference between the gross weight of the raw material and the weight of the purified metal after the removal of surface oxides. This figure includes the metal trapped within the dross itself which is often recoverable through secondary processing.
Smelters use this value to assess the financial efficiency of their melting cycles.
Melt Efficiency
Chemical composition of the furnace environment influences the rate of oxidation on the surface of the pool. A dross loss calculation reveals how much metal is sacrificed to the flame when the oxygen levels are not strictly controlled. Reducing the exposure of the liquid metal to the air lowers the total loss per tonne of throughput.
Flux Interaction
Chemicals added to the furnace assist in separating the oxides from the clean alloy. The dross loss calculation must separate the weight of these added fluxes from the weight of the metal oxides to avoid overstating the actual metal loss. Skilled operators adjust the flux quantity based on the scrap grade to optimize the yield.
Using too little flux results in heavy metal entrapment within the waste layer. When the flux chemistry is incorrect (the separation of the metal from the slag becomes incomplete).
Recovery Cost
Processing the waste material to extract the residual metal requires additional energy and machinery. A dross loss calculation identifies the point where the cost of further recovery exceeds the value of the recovered metal. Most plants sell the raw dross to secondary recyclers who specialize in high pressure pressing or rotary furnace treatment.
