EFFECTIVENESS OF CALCIUM-MAGNESIUM ACETATE AS DUAL SO2-NDX EMISSION CONTROL AGENT

Calcium magnesium acetate (CMA) is an effective dual SO2-NOx emission control agent. Laboratory-scale experiments with dry injected particles at a Ca/S molar ratio of 2 [or (Ca + Mg)/S ratio of 6] resulted in SO2 and NOx removal efficiencies of over 90% at gas temperatures of 950-1,250 degrees C in atmospheres containing 12% CO2, 3% oxygen, 5000 ppm SO2 and 1,000 ppm NOx during a 1-s residence time in an isothermal cavity followed by injection of after-fire air. During the experiments, SO2 reacted with the porous, thin-walled CaO, CaCO3 and MgO cenospheres, formed when CMA calcined, while NO was reduced by hydrocarbon radicals from the organic acetate decomposition. While Ca was the dominant contributor to SO2 reduction by CMA in the isothermal furnace zone, Mg also contributed to SO2 reduction. At gas temperatures less than or equal to 950 degrees C, Mg reacted directly with SO2 in the isothermal furnace zone and was the dominant SO2 remover in the post-furnace quenching zone while indirectly SO2 at higher isothermal zone temperatures by precluding pore-mouth plugging when CaSO4 formed Interactions among hydrocarbons, SO2, and NOx are important but not fully understood.