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Show EXPERIMENTAL Furnace System The experimental studies were conducted in the 2.5 m refractory-lined Control Temperature Tower (CTT). This 25 kW furnace, as shown in Figure 3, is 20.3 cm in diameter and the time/temperature profile can be adjusted using backfired heating channels within refractory walls. The primary fuel, natural gas, was fired at 17.6 kW using a premixed burner. The reburning fuels were injected with a 900 injector located at the centerline of the furnace. This injector allowed the reburning fuel, diluted/transported with argon, to flow radially outward through four 0.5 cm holes and mix rapidly with the oncoming primary effluent. A refractory choke was inserted downstream to isolate the fuel-rich reburning zone from the fuel-lean burnout zone. Burnout air was also injected radially. Analytical Methods Exhaust gas samples were withdrawn through a stainless steel, waterjacketed probe and analyzed for NOx (chemiluminescence). 02 (paramagnetic), CO/C02 (NDIR), and S02 (NDUV). A water-jacketed probe with an internal water quench spray near the front end was used for extracting in-flame samples. Gas phase HCN and NH3 species were collected in a gas washing unit and subsequently analyzed for CN- and dissolved ammonia using specific ion electrodes. Baseline Conditions The baseline conditions for the experiments were: • Primary fuel/natural gas at 80 x 103 Btu/hr; primary NO x, (NOx)p = 240 or 600 ppm (dry, 0% 02) by doping; SRI = 1.1. • Reburning gas injection at 25500F (T1); reburning zone residence time (T2) = 400 ms. • Burnout air injection at 23000F (T2); SR3 = 1.25. 2 |