Magnesium removal from aluminum melts using dichlorodifluoromethane

In this investigation, it was shown that magnesium can be removed from aluminum melts using dichlordifluoromethane (CCI₂F₂). As long as the magnesium content of the melt was greater than 0.5 mass %, the rate of magnesium loss from the bath was a constant, or:$\text{d}\text{(\%}\text{Mg}\text{)}\text{d}\text{t}\text{= −k.}$

For an 850 g melt containing 5 mass % Mg and a gas composition of 10% CCl₂F₂ - 90% N₂, the slopes of the various curves (k) ranged from 4.6 × 10⁻³ %Mg/min at 685°C to 3.1 × 10⁻² %Mg/min at 810°C.

The thermodynamic characteristics of the magnesium removal (‘demagging’) operation were modelled using the F^∗A^∗C^∗T^∗ computer package. Various dross samples generated during the experiments were analyzed by X-ray diffraction in order to confirm the computer predictions.