The Primus process is well adapted for processing dust, which contains more than 5 % of zinc and is typically generated by EAF mini-mills. When fed with EAF dust, Primus produces hot metal of a quality similar to the one produced by a blast furnace, zinc oxide concentrate (more than 55 % Zn) and an inert slag which can be used for road construction.

The Primus process is a two-step process: drying/heating/pre-reduction and final reduction/melting, combining a Multiple Hearth Furnace (MHF) and a specially designed Electrical Arc Furnace to recover valuable metal contents from steelmaking by-products.

The Primus process has been industrially implemented first in 2003 in Luxembourg (for recycling 60 000 tpy of EAF dust) and in 2009 in Taiwan (for processing 100 000 tpy of EAF dust mixed with residues from an integrated mill). The high flexibility of the Primus process allows the joint processing of dust, sludge and scales.