Modeling the Nitrogen and Sulfur Chemistry in Pressurized Flue Gas Systems

A rate-based model is developed to elucidate the chemistry behind the simultaneous absorption of NO_x and SO_x under pressurized conditions (pressures up to 30 bar) that are applicable to the flue gases obtained from CO₂ capture systems. The studied flue gas conditions are relevant to oxy-fuel and chemical-looping combustion systems. The kinetics of the reactions implemented in the model is based on a thorough review of the literature. The chemistry of nitrogen, sulfur, and N–S interactions are evaluated in detail, and the most important reaction pathways are discussed. The effects of pH, pressure, and flue-gas composition on the liquid-phase chemistry are also examined and discussed. Simulations that use existing kinetic data reveal that the pH level has a strong influence on the reaction pathway that is followed and the types of products that are formed in the liquid phase. In addition, the pressure level and the presence of NO_x significantly affect the removal of SO₂ from the flue gas.