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Show Having benchmarked the effects of global staging on ftring system performance, both vertical and horizontal staging techniques within the main ftring zone were subsequently tested to evaluate their effects on NOx performance. The objectives of this work were to conftrm the results of prior main windbox vertical air staging work, and to further reduce outlet NOx emissions from the previously demonstrated "best" level of 0.13 poundslMM Btu through the application of horizontal, and integrated vertical and horizontal main windbox staging techniques. As such these methodologies were applied in concert with the "optimized" TFS 2000™ frring system, keeping the global stoichiometry history constant to allow meaningful comparisons. First, vertical air staging within the main windbox was independently varied to demonstrate its effect on NOx formation at this large pilot scale. Results from this testing, given in Figure 2, show that significant variation in NOx emissions occur as main windbox vertical air staging is changed. In this case variations to the vertical air staging produced a +/- 13% deviation in outlet NOx about the mean. This result confrrms that the main windbox vertical stoichiometry history is an important contributor to overall NOx formation, even with significant levels of global air staging. Overall, NOx emissions increased when variations to the main windbox vertical stoichiometry build-up were applied to the previously "optimized" TFS 2000™ arrangement. This result is, however, expected since the "optimized" TFS 2000™ system incorporates the results of prior chemical kinetic modeling and small scale combustion test vertical air staging work into the configuration of its main windbox as noted above. Next, horizontal staging used to control the horizontal "build-up" of stoichiometry (comer to comer) within the main burner zone, was evaluated. This was accomplished by biasing the fuel and air between one or more of the four comers. Tested subsets of this technique are two comer frring, where all of the air and fuel are injected through two of four comers in a tangential arrangement, and opposed comer frring where the coal is injected from two comers, and the air from the remaining two. In general, independent implementation of horizontal staging techniques resulted in neutral to degraded NOx emissions performance over that of the "optimized" TFS 2000™ firing system during the subject testing. This is seen in Figure 3, which shows the effect of independent variation of either fuel or air (horizontal staging) on overall NOx emissions performance. These results demonstrate that, similar to the prior vertical staging experiments, outlet NOx emissions can be affected by horizontal fuel and air distributions. However, these results also demonstrate that the global time - stoichiometry history (i.e. , the TFS 2000™ stoichiometry profile) dominates the NOx formation and reduction processes at these levels of global air staging. Finally, several configurations which applied integrated vertical and horizontal staging techniques as a means of "optimizing" the stoichiometry of combustion within the main windbox were evaluated. Integrated vertical and horizontally staged frring systems were extensively evaluated using CFD modeling prior to the BSF tests. In contrast to their independent performance, Figure 4 shows that when suitably combined, an integrated vertical and horizontal staging strategy offers a small, but consistent improvement to the NOx emissions performance of the optimized TFS 2000™ system. At a NOx emission level of 0.1 1 poundslMM Btu, the "best" integrated system ("Integrated Config. 6") produced a greater than 10% reduction in NOx over the previously "optimized" TFS 2000™ system. Carbon loss results (not shown) were also similar for the two firing systems. Additional pilot scale testing of potential NOx control subsystems in the BSF has been recently completed and results are being analyzed. The objective of this testing was to confirm the performance of the integrated vertical and horizontal staging technique, focusing on the repeatability of the present test results, while generating design information for this and other promising firing system concepts for eventual full scale utility boiler application. CATALYTIC FILTER OPTIMIZATION Introduction: The principal goal of the Catalytic Filter Optimization activities is the acquisition of initial field test data, which will be used for a larger field demonstration. These activities include the determination of feasible and reasonable operating conditions for the catalytic filter system. Data collected through testing will focus on particulate and NOx removal efficiencies as well as filter draft loss. |