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Show 11 could have been improved further with additional testing. More importantly, the gradient in NO emissions was reduced to only 20 ppm (390 to 410 ppm) as shown in the bottom half of Figure 9 and even more dramatically in Figure 10. The average O2 level of 2.60/0 operating under balanced O2 and optimized NOx conditions was higher than the 1.80/0 O2 low spot that dictated the lowest acceptable O2 and furnace conditions in the "as found" initial baseline. Therefore, a much lower overall O2 level and NOx emissions than that shown in Figures 9 and 10 could be achieved with an additional 0.6 to 0.80/0 reduction in the average O2• Unfortunately, it was not possible to demonstrate this potential benefit because the boiler O2 controller was operating at the "minimum air stop" and an instrumentation technician was not available to reset the stop necessary to conduct a lower O2 test. It should be noted that the real time multi-point gaseous emissions analyzer shown in Figure 7 is currently equipped only to measure 0 21 although the software and data acquisition system could easily be extended to measure NO and CO emissions as well. (The NO emissions contours in Figures 9 and 10 were generated by sequential measurement at each probe location using a TECO chemiluminescent NOx analyzer.) A real time multi-point O2, NOx, and CO advanced combustion diagnostics instrumentation system would have numerous benefits compared to the current multi-point O2 system. Combustion tuning to minimize NOx emissions could be performed directly in real-time without inferring the results through O2 measurements. NOx corrected to 3% O2 would minimize the uncertainty associated with air infiltration on balanced draft units. CO emissions data would be valuable in spotting low O2 regions on reactive coals where a CO threshold can be used to establish the lowest local minimum O2 level. A preliminary design of a multi-point O2, NOx, and CO instrument has been prepared and an informal market assessment is being conducted to determine the interest on the part of utilities concerning the potential uses of the instrument for NOx emissions diagnostic and optimization testing. Another advanced instrumentation technique that aids in combustion diagnostics and boiler performance optimization is the HOT FOIL ® LOI analyzer recently developed by Fossil Energy Research {Figure 11 f. This instrument virtually eliminates one of the most common frustrations of boiler testing, the several day to one week or more delay in obtaining the LOI test results from a boiler emissions and performance test. With this instrument, it is possible to determine the ash LOI value within 10 or 15 minutes from the time the sample probe was removed from the duct. Unlike the very expensive on-line LOI analyzers that typically sample from only one point in a duct, a representative ash sample is collected manually from several sample ports using an inexpensive high volume ash collection system. The sample is immediately removed from the filter and placed on a metallic foil heating element that first drys and then incinerates the ash sample. The LOI is determined in the conventional manner by comparing the sample weights before and after heating to define the weight loss. • Manufactured and sold under EPRI license. |