Pressing of skimmed hot drosses in a press is a very popular technology for cooling hot dross and obtaining the maximum in-house recovery of aluminum alloy. As a result of the pressing action, part of the molten aluminum alloy is squeezed out, while the rest of the free metal remains in the pressed skulls. Thus, pressed skulls are a valuable waste product, consisting of 30-70 wt. percent free aluminum. Other constituents are aluminum oxide and oxides of alloying metals. Pressed skulls are generally valued on a free-metal recovery basis, which necessarily involves practical determination of their free aluminum content. Because most analytical methods are limited to the laboratory level and representative sub-samples, there is a practical interest in developing a routine, cost-effective, and non-destructive method to predict the free aluminum content in entire pressed skulls, based on their density. To develop such a method, a relation between the bulk density, porosity, and free aluminum content of pressed skulls was established. This article offers a review of those experiments and an analysis of their results.
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