Mechanisms and processes for sustainable primary synthesis

For primary metals, sustainable metallurgy focuses on replacing carbon‑based reductants and fossil heat with hydrogen, hydrogen‑bearing carriers, electricity, and plasma, while re‑engineering the reaction path and microstructure evolution to maintain throughput and quality. In ironmaking, this includes direct reduction of hematite and other iron oxides with H₂ or H released from ammonia, followed by electric melting and refining; here, H₂O replaces CO₂ as the main reduction by‑product, and the main challenge moves to supplying green hydrogen and designing reactors that manage gas‑solid transport, sticking, and sintering. Hydrogen‑based plasma reduction goes a step further by using ionized hydrogen to reduce oxides in a single high‑temperature step that merges calcination, smelting, reduction, and initial alloying, enabling near‑stoichiometric use of reductant and high metallization degrees at short residence times.

For high‑CO₂ metals such as Ni and Co, hydrogen‑plasma‑based reduction can bypass long multistage hydrometallurgical sequences by directly reducing lateritic or mixed oxides to high‑grade ferronickel or other alloys in one furnace step, with rapid liquid‑state reduction and phase partitioning into metal and slag. Similar principles apply to plasma‑based recovery of metals from complex waste streams, where non‑equilibrium plasmas, steep thermal gradients, and tailored slag chemistries are exploited to selectively volatilize, dissolve, or segregate different elements. Across all these processes, materials science controls reduction kinetics (nucleation, growth, percolation of metallic networks), defect formation, and impurity partitioning, which in turn govern both energy consumption and downstream alloy properties.