Melt Oxidation and Heavy Dross in Secondary Aluminum Processing: Sealed Refining with Box‑type In‑line Degassing Unit

Secondary aluminum feedstock features complex composition. Scrap surfaces carry oxide films, oil, and moisture. Once melted, these impurities readily react with ambient air and generate large volumes of oxide dross. Floating dross increases manual skimming workload, blocks melt homogenization, and raises the risk of re-hydrogen absorption.

Conventional open melt treatment vessels expose molten aluminum directly to air and cannot restrain oxidation. For continuous secondary aluminum lines running at 25–35 t/h, persistent dross formation undermines consistent melt quality and raises casting defect risks.

The FDUII-30 fixed box-type dual-rotor degassing unit adopts a sealed chamber with inert gas protection for continuous secondary aluminum melting and casting. Dual rotors disperse Ar or N₂ bubbles evenly into molten aluminum for hydrogen removal. The inert atmosphere inside the chamber isolates air contact and suppresses fresh oxide dross generation. The unit is installed in-line without interrupting continuous scrap aluminum production.

Source: Document "Dual-rotor In-line Degassing Parameter Sheet"

The chamber is lined with monolithic sintered CV8 refractory castable, featuring erosion resistance and stable sealing performance. Submerged inlet and outlet ports reduce liquid turbulence and air entrainment. Multi-circuit gas control maintains inert atmosphere during production idle periods to prevent melt oxidation during shutdowns.

Hydraulic 0–180° rotating structure enables chamber opening for inspection and dross cleaning, balancing sealed operation and equipment maintenance.

The sealed degassing unit suppresses new dross formation but cannot remove solid dross carried from upstream processes. Secondary aluminum foundries shall pre-treat scrap feedstock to reduce incoming contaminants. Stable inert gas supply and periodic sealing surface inspection are required to preserve the protective environment inside the chamber.