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Show Modifications to the main windbox were also required. After removing the existing burner pipes and air nozzles, the partition plates and windbox turning vanes were inspected for warpage and general wear. When necessary, these parts were replaced or refurbished. All of the partition plates were cut back approximately three inches to allow greater tilting mobility of the new coal and air nozzles. The offset air nozzles in the main windbox have the capability to move in the horizontal direction by a manual adjustment (Figure 4). The air nozzles and coal nozzles are tilted in unison using automatic controls. LNCFS Level II Characterization. After the retrofit to install LNCFS Level II, the fine tuning and initial adjustments were accomplished. Following these tests by ABB CE, diagnostic and performance tests were conducted. To date, 28 diagnostic and 7 performance tests have been completed. These tests were conducted in a manner similar to those conducted during the baseline characterization tests. The results of these tests are presented in comparison to the baseline tests in Figure 9 which shows the LNCFS Level II and baseline NOx emissions as a function of load. These results show that, unlike the baseline results. unit NOx emissions increase as unit load decreases. This can be attributed to the operation of the SOFA system. At full load. the dampers in the SOFA are open 100 percent. However. as unit load is decreased. these are closed until there is no overfire air at minimum load. Figure 10 shows the baseline and LNCFS Level II CO emissions for this unit. Baseline CO emission maintained a tight band in the 5 to 20 ppm range. Post retrofit CO emissions were not as predictable. CO emissions with LNCFS Level II are highly dependant upon unit excess oxygen levels. As the excess oxygen level decreases. unit CO emissions increase. During some tests. reductions of only 0.75 percent in excess oxygen levels have caused CO emissions to increase over 60 ppm. A pre- and post-retrofit comparison of combustibles loss-on-ignition values is not available at this time. As stated previously. the objective of this project is to determine the long-term NOx emissions for aT-Fired boiler. Long-term data collection is the definitive method to determine the actual NOx reduction characteristics of a low NOx combustion system. Although the entire long term data set for LNCFS Level II has not yet been collected. Figure 11 compares the average long-term NOx emissions for LNCFS Level II to the baseline emission levels. These data show that at full load (200 MW), the unit is able to meet a 0.45 Ib/MBtu standard for NOx emissions with an emission level of 0.39 Ib/MBtu. However. this is not the case for low load operation. NOx emissions during off peak hours when the unit is at minimum load are well above the 0.45 lb/MB tu limit. At the minimum load of 55 MW. NOx emissions exceed 0.60 Ib/MBtu. VI. FUTURE ACTIVITIES Wall-Fired Boiler Phase III testing is scheduled for July 1991 through March 1992. During this phase, evaluation of the emissions and performance of the boiler will be performed while operating the LNBs with and without the AOF A. T -Fired Boiler Phase II long-term testing of LNCFS Level II is in progress and will be completed in October 1991. LNCFS Level III is scheduled for installation during an outage in November and will be tested following the retrofit LNCFS Level I will be tested in mid-1992 by shutting off the air flow to the SOFA system. ACKNOWLEDGEMENTS The authors wish to gratefully acknowledge the support and dedication of the following personnel for their work at the wall-fued test site: Mr. Ernie Padgett. Georgia Power Company, and Mr. Mike Nelson, Southern Company Services, for their coordination of the design and retrofit efforts and Mr. Jose Perez. Instrumentation Specialist 13 |