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Calcium magnesium acetate has been assessed as an agent for the reduction of NOx, SO2, and HCl, at the pilot scale, in a down-fired combustor operating at 80 kWth. In addition to this, the chemical and physical processes that occur during heating have been investigated. Benchmarking of calcium magnesium acetate with a suite of five other carboxylic salts (calcium magnesium acetate, calcium propionate, calcium acetate, calcium benzoate, magnesium acetate, and calcium formate) has been performed. NOx reduction involves the volatile organic content of the carboxylic salt being released at temperatures of >1000 °C, where the reaction of CHi radicals with NO under fuel-rich conditions can result in some of the NO forming N2 in a "reburning" process. Thermogravimetry-Fourier transform infrared (TG-FTIR) studies identified the nature of the decomposition products from the low-and high-temperature decompositions. In addition, the rate of weight losses were studied to investigate the influence of the organic decomposition on NOx reduction by reburning. In-furnace reductions of SO2 and HCl are aided by the highly porous, particulate residue, which results from the in situ drying, pyrolysis, and calcination processes. Simultaneous reduction of all three pollutants was obtained, and a synergy between SO2 and HCl capture was identified. A mechanism for this inter-relationship has been proposed. Sorbent particle characterization has been performed by collecting the calcined powder from a spray pyrolysis reactor and compared with those produced from a suite of pure carboxylic salts. Physical properties (including porosity, surface area, and decomposition behavior) have been discussed, relative to reductions in NOx and acid gas emissions. TABLES AND FIGURES

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The technique of combustion modification by air staging (over-fire air) for the control of NO x emissions is currently implemented in many coal-fired power stations. This paper presents results from a new process involving the injection of calcium magnesium acetate (CMA), which can reduce SO 2 and at the same time enhance NO x reductions above those achievable by air staging alone. The experiments were performed in a 3.5m long, horizontal tunnel furnace with an internal diameter of 500 mm operated at 80 kWth by firing gas-oil. The organic content of CMA behaves like a fuel, and the Ca content calcines principally to CaO for acid gas capture in the furnace at temperatures greater than 1000 °C. The solubility of CMA in water means that concentrated solutions can be sprayed into the furnace as a fine mist, giving the possibility of intimate mixing with combustion gases. The concentration of fuel nitrogen in the fuel could be easily modified by varying the amount of dopant (quinoline) injected into the oil feed to simulate typical levels of NO x emission. SO 2 concentrations were set by injecting SO 2 gas into the combustion air. NO x reduction studies were performed at staging levels which created near-burner zone stoichiometries (λ nbz ) of 1.18 (3% O 2 dry) at 0% staging to 0.64 at 46% staging. Over this range of staging levels, the injection of CMA improved the reduction of NO x by a further 25-35% for an initial NO x level of 450 ppm at an overall stoichiometry of λ 1 ) 1.18. The effect of CMA on NO x reduction was more apparent at lower levels of staging because of higher initial NO x levels. The near-burner zone (nbz) stoichiometry was 0.64 at this condition. SO 2 reductions were studied up to a Ca/S ratio of 2.25, where reductions in the region of 80% were achieved for initial levels of 940 ppm.