ABSTRACT
The effect of water (H2O(g)) on in situ SO2 capture using limestone injection under (FBC) conditions was studied using a thermobalance and tube furnace. The indirect sulphation reaction was found to be greatly enhanced in the presence of H2O(g). Stoichiometric conversion of samples occurred when sulphated with a synthetic flue gas containing 15% H2O(g) in under 10 h, which is equivalent to a 45% increase in conversion as compared to sulphation without H2O(g). Using gas pycnometry and nitrogen adsorption methods, it was shown that limestone samples sulphated in the presence of H2O(g) undergo increased particle densification without any significant changes to pore area or volume. The microstructural changes and observed increase in conversion were attributed to enhanced solid-state diffusion in CaO/CaSO4 in the presence of H2O(g). Given steam has been shown to have such a strong influence on sulphation, whereas it had been previously regarded as inert, may prompt a revisiting of the classically accepted sulphation models and phenomena. These findings also suggest that steam injection may be used to enhance sulfur capture performance in fluidized beds firing low-moisture fuels such as petroleum coke.
