Replacement of Fossil Carbon in the Ferroalloy Industry, Striving for CO2 Neutral Ferrochrome Production

To counteract the consequences of anthropogenic climate change, the decarbonization of CO2 intensive industries is necessary. Metallurgical processes are responsible for a considerable proportion of industrial CO2 emissions. One approach to avoid direct emissions is the substitution of fossil carbon carriers through alternatives with a lower CO2 footprint. This dissertation investigates the decarbonization of ferroalloys using ferrochrome as an example. Ferroalloys are produced in electrically operated smelting reduction furnaces or occasionally in blast furnaces. Coal and coke from fossil sources are used as reducing agents to produce high carbon ferroalloys or ignoble metals such as aluminum or silicon are used as reducing agents to produce high-quality low carbon ferroalloys. To produce carbon-containing ferrochromium, this work compared potentially CO2 neutral carbon carriers from biogenic raw materials with metallurgical coke. The processes investigated were chromite melting with fluxes and reducing agents in a laboratory electric arc furnace and chromite pre-reduction followed by a melting step. Thermochemical modeling was carried out to aid the design of a fluxing strategy and to determine key performance indicators of the process. The production of low carbon ferroalloys was investigated using silicon and silicon carbide-containing residues from the solar industry in a laboratory electric arc furnace as an alternative to silicon-containing alloys. As for the carbothermic reduction, thermochemical modeling was carried out to quantify key performance indicators of the process.