Chemical Interactions between Potassium, Sulfur, Chlorine, and Carbon Monoxide in Air and Oxy-fuel Atmospheres

Abstract

This paper presents experimental and modeling work on the interaction between the K, Cl, and S components, and these chemical interactions are studied in both air-fuel and oxy-fuel atmospheres. Detailed kinetic modeling is conducted to examine the potassium chloride sulfation and its interaction with CO oxidation in both nitrogen- and carbon-dioxide-based atmospheres. The oxidation of CO enhances the kinetics of alkali sulfation for typical post-flame conditions, below 1000 °C, in both atmospheres. For higher temperatures, sulfation kinetics are promoted even further in CO2-rich atmospheres. Oxy-fuel atmospheres, i.e., CO2-rich atmospheres, also promote increased levels of CO in technical-scale flames. Therefore, in practical systems, enhanced sulfation kinetics will automatically be promoted by flue gas recirculation. Also, the availability of sulfur, in the form of an increased SO2 concentration, often enables complete sulfation of alkali in oxy-fuel atmospheres as a result of the flue gas recirculation. The availability of SO3 may increase in oxy-fuel compared to air-fuel atmospheres as a result of either elevated SO2 levels or different sulfation reaction patterns, as discussed in the modeling of this work. However, SO3 has no significant impact on the overall sulfation rates in oxy- compared to air-fired systems.