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Show furnace outlet temperature as well. Lastly, CCTFS incorporates a new concept of clustered coal nozzles which maximize the separation of the fuel and air in the early stages of combustion. The combination of these features allows the firing system to achieve very low NO emissions with minimal impact to the boiler. x CCTFS was developed by ABBjC-E on the basis of large 15 MWt (50 MBtu(hr) pilot scale testing at the Boiler Simulation Facility (BSF) located at ABB C-E's Kreisinger Development Laboratory in Windsor, Connecticut, USA (Figures 2 and 3). These tests were performed under conditions which replicated the aerodynamic and thermal conditions of a large utility boiler. The BSF has six (6) elevations of corner-located tangential coal nozzles. It models all the major aspects of a utility boiler including the lower furnace, the ash hopper, the burner zone, the arch section, and the upper furnace heat transfer surfaces. This facility provides a technically superior means of studying complex firing system related phenomena in a controlled and cost effective manner. COAL FIRING RESULTS BSF Testing Several different CCTFS configurations were evaluated by ABBjC-E . Extensive tests were performed with an American eastern bituminous coal having similar characteristics to the coals utilized by ENEL in terms of fixed carbon-to-volatile ratio, nitrogen content, ash fusion temperature, etc. Some of the important results from the CCTFS (15 MWt) laboratory testing program were : o Gradual staging appears to be more effective in reducing NO emissions than a single OFA zone. The optimum split betwee~ the OFA elevations is both coal type and unit specific . o For the same percent OFA, the OFA velocity and yaw (horizontal angle ) have a significant effect on NO , CO, and unburned carbon emissions . x o The grouping of coal nozzles into "clusters" reduced NO emissions by x 10% to 15% at normal excess air levels (2 . 5% 0 to 3.5% 0 ) and moderate levels of OFA (20%); see Figure 4. A~ high quan~ities of OFA, the clustering technique has little effect on NO. Clustering is of value at reduced loads where deep staging is no~ practical and for existing units where slagging will inhibit the maximum use of deep staging. o ENEL's target NO emissions level of 400mgjNm3 @6% O 2 ( . 32 lb j MBtu or 240 ppm @ 3% 02)xwas achieved with 30% OFA while operating at an excess air level of 3% to 4% O 2 with no statistical increase in unburned carbon emissions. Thls was a 50% reduction from the baseline NO emissions of 510 ppm . Reductions of greater than 50% were possible at higher OFA quantities. Fusina Station CCTFS Demonstration Based on the promising results of the laboratory program, a prototype CCTFS low NO firing system was designed and installed in ENEL's 160 MW Fusina unit ~2, a multi-fuel (coal, oil, gas) ABB C-EjF.T.C. tangential design boiler located near Venice, Italy (Figure 5). Modifications to the 3 |