EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Flue gas recirculation (FGR) has been proposed as a process improvement for ferrosilicon production, with the aim of increasing the CO2 concentration in preparation for carbon capture and storage or use. By replacing cold ambient air with warm recirculated flue gas, the potential for energy recovery is also increased. Reducing the concentration of oxygen in the combustion air is also expected to limit peak temperatures and reduce production of thermal NOx. A pilot scale experiment was conducted to evaluate the effects of FGR. The off-gas system of a 400 kVA one phase furnace was modified to allow for flue gas recirculation. Typical industrial raw materials were used throughout the 48-hour smelting experiment. Analysis of combustion air and flue gas was performed using FTIR and GC analysis. Measurements of total organic compound content in the gas was carried out along with gas sampling for further PAH analysis. Samples of silica were taken and investigated. FGR ratios investigated were 0, 25, 50 and 75 % with varying amounts of flowrates from the furnace hood. Several flow and temperature measurements in the off-gas system, combined with the gas analysis, enabled a detailed mass and energy balance of the system. In this work, we will highlight the principal results from the measurement campaign and further discuss the applicability of FGR to the Si-process. Special attention is given to NOx and PAH emission.