Effect of atmosphere on the release behavior of alkali and alkaline earth metals during coal oxy-fuel combustion

Understanding the effect of the atmosphere on the release of alkali and alkaline-earth metals (AAEM) during oxy-fuel combustion is important for the development of oxy-fuel combustion technologies with reduced problems with particulate formation and corrosion. To this end, we examined the release behavior of AAEM during oxy-fuel combustion in different gas environments. A drop-tube reactor and ion chromatography were used to investigate the release rates of AAEM. Our results show that the release rates of Na and K were higher than those of Ca and Mg in all types of gas environments. Experimental conditions that favor combustion, namely, higher temperature, higher oxygen content, and longer residence time, markedly increased the release rates of Na and K, whereas changes in the release rates of Ca and Mg were much smaller. The presence of SO2 in the atmosphere suppressed the release of AAEM via formation of sulfates, whereas the presence of H2O promoted it. A synergistic effect of H2O and SO2 on the release of AAEM during oxy-fuel combustion was observed.