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Show large utility boiler. 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; providing a technically superior means of studying complex firing system related phenomena in a controlled and cost effective manner. COAL FIRING RESULTS FROM BSF TESTING Several different CCTFS configurations were evaluated by ABB C-E. Extensive tests were performed with a U.S. 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 Multi-level introduction of overfire air (OFA) appeared to be more effective in reducing NO emissions than a single level x configuration. The optimum location, size, and nozzle arrangement of the OFA injection points is both coal type and unit specific. o For the same quantity and location of separated OFA, the OFA velocity and yaw (horizontal angle) had a significant effect on NO , CO, and x unburned carbon emissions. o The grouping of coal nozzles into "clusters" reduced NO emissions by x 10% to 15% at normal excess air levels (2.5% O 2 to 3.5% O 2 ) and moderate OFA flow rates (20%). At high quantities of OFA, the clustering technique has little effect on NO. Clustering is of x value at reduced loads where deep staging is not practical and for existing units where slagging will inhibit the maximum use of deep staging. o ENEL's target NO x emission limit of 400 mg/Nm3 @6% O 2 (0.32 lb/MBtu or 240 ppm @ 3% 02) were achieved with 30% OFA while operating at an excess air level of 3% to 4% O 2 with no statistically significant increase in carbon emissions. This was a 49% reduction from the 4 |