Zero Emission Silicon and Manganese production through electrowinning

CO2 is an unavoidable by-product from silicon and ferroalloy production in current industrial practice. ZeSiM will eliminate CO2-emissions from manganese ferroalloy and silicon production by replacing carbon with renewable energy in the most direct way possible: through electrowinning. Replacing carbon with electricity requires a higher energy consumption, but when using a carbon free electric energy source, the goal of zero CO2 emissions can be reached. The electrolysis process results in production of oxygen gas and relatively pure metals, reducing the need for metal refinement. In the ZeSiM project, we suggest developing CO2-free electrolysis processes for manganese ferroalloys and silicon along two different paths. 1) Production of liquid manganese or manganese ferroalloys from manganese oxide using an oxide-based electrolyte. Advantages include a potential for high production rate, utilization of fine-grained materials, and producing the marketable product low carbon ferromanganese (LCFeMn) directly. 2) Producing solid silicon plates directly from quartz using a chloride/oxide electrolyte. Advantages are low-cost chemicals, easily harvested product, and relatively low temperatures. ZeSiM will focus on challenges and knowledge needs related to the electrolysis processes like electrolyte chemistry, metal quality and energy consumption. Expertise gained through the project is an important step before research and development can be done on materials selection. All-electric production of silicon and manganese would represent a step-change in the decarbonization of Norwegian ferroalloy production, eliminating all process-related CO2-emissions. The products would be globally unique, and attractive as alloying elements in green steel and aluminium. SINTEF is the project manager with NTNU as a research partner. Si/FeSi producers Elkem, Wacker and Finnfjord and Mn-alloy producer Eramet are industrial partners through The Norwegian Ferroalloy Research Association (FFF)

Reducing CO2 emissions from human activity is the main measure to reduce global warming and meet the climate goals. CO2 is an unavoidable by-product from silicon and ferroalloy production in current industrial practice. ZeSiM will eliminate CO2-emissions from manganese ferroalloy and silicon production by replacing carbon with renewable energy in the most direct way possible: through electrowinning. SINTEF is the project manager with NTNU as the second research partner. The industrial Si and FeSi producers Elkem, Wacker and Finnfjord and Mn-alloy producer Eramet are industrial partners through The Norwegian Ferroalloy Research Association (FFF). Manganese ferroalloys and silicon are important alloying additives in steel and are today produced efficiently by carbothermic reduction in Submerged Arc Furnaces (SAF), emitting 0.9-1.3 kg CO2/kg Mn ferroalloy and 5 kg CO2/kg Si as process reaction products. All-electric production of silicon and manganese would represent a step-change in the decarbonization of Norwegian ferroalloy production, completely eliminating all process-related CO2-emissions by instead producing oxygen. The products would be globally unique, and attractive as alloying elements in green steel and/or green aluminium. In the ZeSiM project, we suggest developing CO2 free electrolysis processes for Mn and Si along two different paths: i) Electrolytic production of liquid Mn ferroalloys from MnO in a molten oxide electrolyte and ii) Si electrolysis from quartz in a molten chloride-based electrolyte. ZeSiM will address challenges and knowledge needs related to electrolyte chemistry, oxygen evolution, energy consumption, and optimalisation of the electrolysis parameters. Theoretical and thermodynamic assessments, electrochemical measurements, and electrolysis trials as well as material characterization methods will be applied. Risk mitigating actions are to use materials reported in literature and fluoride additions to obtain better electrolyte properties.