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Show 4 magnetic analyzer. The NH3 and HCN concentrations were analyzed by an ion-selective electrode. Unburnt carbon in fly ash was analyzed using a thermogravimetric analyzer, and the coal burnout was calculated based on the ash balance method. The gas temperature in the furnace was controlled by the outer electric heater and measured with a Pt-Pt/13% Rh thermocouple installed in the inlet of the sampling probe. 1 'ry Air + Coal , Burner (Coal : 2g/min) 2'ry Air (+N~~---tl~...,' / Heater (max.1600CC) Coal Feeder Cyclone Flue Gas Fig.3 Schematics of Drop Tube Furnace (DTF) Some characteristics of the coals tested are presented in Table 1. Coal A and B are high volatile bitumious coals, and coal C and D are middle and low volatile bit,umious. Coal E is semi-anthracite, and coal F is anthracite. The fuel ratios of these coals range from 1.0 to 11. The particle size distri~utions for all coals were about 80% through 200 mesh (74 f..l rn). Both a laser diffraction particle sizer and wet sieves were used for the measurements of the particle size distributions. The rate of coal injected was kept constant at about 2 g/min (heat input: about 13 kcaVrnin), controlled by the rotary feeder. To obtain the reaction rates of volatile evolution and NOx formation, tests were performed under the oxidation conditions in the furnace. On the other hand, for the reaction rate of NOx reduction, measurements were made under the reduction conditions in |