Overview: OS Process – I. Fundamental

The authors proposed direct reduction from metallic oxides to their metals in 2000–2003. This concept was firstly applied for direct reduction of TiO2, and called the OS process in comparison with FFC Cambridge process. Both processes commonly used the CaO-CaCl2 melt, the electrolysis with the carbon anode, and TiO2 as the starting oxide. OS process is designed as a 1-pot operation, the combination of thermal reduction by Ca in CaCl2-CaO melt and the simultaneous electrolysis of the byproduct CaO to form metallic Ca. O2− is extracted as CO/CO2 gas from the carbon anode, and Ca2+ forms Ca (dissolved as the metallic state in the molten salt). This reducing environment near the cathode is suitable for metal formation from various oxides. This overview (part I) summarizes the basic concept of OS process, and the subsequent overview (part II, III) will report its experimental confirmation and its applications, respectively.