Pilot-Scale Test of Flue Gas Recirculation for The Silicon Process

Flue gas recirculation (FGR) for the silicon process may facilitate increasing the CO₂ concentration in the off-gas, which will be beneficial for potential future carbon capture. Lower oxygen concentration in the combustion gas will also reduce NO_x emissions. An existing 400 kVA Submerged Arc Furnace (SAF) pilot setup was modified to be able to recirculate flue gas and equipped with gas analysis to monitor both the flue gas and the mixed combustion gas entering the furnace. Over a running period of 80 h, including 32 h of startup, twelve different combinations of FGR ratios and flow rates were tested using typical industrial raw materials. Increased CO₂ flue gas concentrations were successfully demonstrated with concentrations over 20 vol % CO₂. Emissions of NO_x were shown to be reduced when isolating stable comparable periods within each tapping cycle.