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Show Short-Term Load Range NOx Characteristics llOO~--------~--------~--------~----------~=== 1 000 +----------+----------1~ • Phase I • Phase II 900+-----~ 800 +-----6- NOx, ppm Increasing (3% 02) 700 +--_0_2_-+- 6OO~----~~~~~~~~-r----~~~~~--~~~~----4W--~ Increasing 02 400+----------+----------+----------+----------+---------~ 250 300 350 400 450 500 Gross Load, MWe Figure 5: Plant Hammond Short-Term Load Range NOx Characteristics Table 2 Phase I Long-Term Testing - Daily Average NOx Emissions Number of Daily Values 52 Average Emissions (lb NOx/MBtu) 1.16 Standard Deviation (lb NOx/MBtu) .11 Distribution Normal Achievable Emission Limit (lb NOx/MBtu) 1.24 Advanced Overfire Air Characterization. Prior to the start of the AOFA characterization. substantial effort was expended to optimize the existing pre-NSPS burners. This was accomplished by iteratively adjusting burner registers while monitoring combustion emissions and distribution. It was determined that very small changes to many of the burners created large changes in the emissions characteristics. It is anticipated that retrofit of the burner air registers during Phase III will allow more balanced secondary air flow to each burner. Following the burner optimization, a cursory characterization of the AOFA system hardware was conducted. This process involved initial tests to open and close the various AOF A dampers during plant operation. After the initial tests, the AOFA system was subjected to the diagnostic, performance, and long-term testing described previously while monitoring emissions, slagging, carbon carryover. and operating stability. Boiler operation was nominal with the AOFA system in operation and frequent inspections of the boiler walls showed no abnormal slagging conditions. A graphical comparison between baseline and AOFA diagnostic. performance. verification and long-term tests results is given in Figures 5 and 6. These results from the AOFA operation show a substantial reduction (up to 40 percent at full-load reducing to 25 percent at 300 MW) in NOx emissions when comparing short-term tests. However. long-term tests comparisons indicate a maximum NOx emissions reduction of only 25 percent. These differences between short-term results and long-term results are not unexpected. The long-term testing provides emission and operational results that include most. if not all. of the possible influencing parameters that can affect NOx emissions. These parameters include coal variability, mills-in-service patterns. mill bias ranges, excess oxygen excursions, equipment conditions. operator variability, and as yet undetennined influencing parameters. Results from this long-term testing provide a true representation of the emissions of the unit while short-tenn 9 |