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Show unit were completed in late 1989 and included : 1) clustered coal nozzles (two groups of two each), 2) overfire air (OFA) , both as close-coupled OFA (at the top of the windbox) and 3) separated OFA at a higher elevation supplied with a boost fan to study the effect of high velocity OFA , and lastly 4) concentric firing auxiliary air nozzles with variable horizontal angle. To date several coals (high and low volatile) have been tested with encouraging results . The following initial NO emissions goals of the x program have been achieved : coal firing: 3 400 mg/Nm @ 6% O 2 (240 ppm @ 3% O 2 ) 8% unburned carbon Increased coal fineness has been required to avoid higher unburned carbon levels . Typical premodification (no OFA) emissions were; coal firing : 850 mg/Nm 3 @ 6% 0 (510 ppm @ 3% O 2 ) 7-8% unbusned carton oil firing: 650 mg/Nm @ 3% O 2 (320 ppm @ 3% O 2 ) Future tests will evaluate oil and natural gas firing . OIL AND GAS LOW NOX FIRING RESULTS FROM BSF Further laboratory tests were performed at the Boiler Simulation Facility (15MWt scale) to quantify the effects on emissions, combustion efficiency and heat release profile resulting from the application of combustion technique NO control schemes for oil and gas firing in a multi-fuel coal-capable~oiler. The experimental coal firing CCTFS was modified to also fire oil and gas by replacing the appropriate auxiliary air compartments with oil/gas/air compartments .that replicated typical commercial ABB C-E design (see Figure 6). Separate tests were performed with natural gas and a heavy fuel oil (No . 6 with approximately 0.3-0.4% N) . The tests parametrically investigated: o Separated OFA (flowrate, velocity, injection angle(s), elevation(s» o Close-coupled OFA o Flue gas recirculation (FGR) (through hopper, through windbox ) o Excess air o Windbox air distribution o Concentric air firing (CFS) o Load Gas Firing Results The results obtained during natural gas firing tests are shown in Figures 7, 8 , and 9 . Baseline NO x emissions were 70 ppm (corrected to 3% O 2 ) at 4 |