Abstract
Producing high-silicon alloys in submerged arc furnaces (SAF) involves the generation of an intermediate process gas, consisting of silicon monoxide (SiO) and carbon monoxide (CO). Combustion of process gas from the taphole can be an environmental challenge. SiO gas burns to fine SiO2 particles which can cause poor working conditions and fugitive particulate matter emissions. The high combustion energy of SiO and CO is a source of high heat load. It is also the source of thermal NOx generation. A measurement campaign was conducted at the Elkem Thamshavn plant in Norway to investigate the composition of tapping gas from a silicon furnace. Over a 3-day period, the gas extracted from the tapping of the furnace was analyzed with Agilent Micro-GC, Protea atmosFIR, and Testo 350. The dust concentration in the gas was measured with a LaserDust instrument from NEO Monitors. Using the plant’s existing flow and temperature measurements, mass and energy flows were calculated. Linear regressions were calculated for three predictors of NOx formation in the taphole gas. From these calculations, the relation between total energy added to the tapping gas and NOx showed the best correlation.