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Show Based on these results, recommended parameter settings were established for best NOx emission level and best heat rate at full load operation (Table 1). The main damper opening was reduced more than a third for each and significant changes were also made to the burner tilts. Figure 3 shows the NOx profile and Figure 4 the heat rate profile over the course of the 81 tests. The software provides an analysis of the relative influence of each control parameter on each output variable. This knowledge of the most important control parameters in the optimal operating region is an aid in initial development or modification of combustion control strategy. Prediction accuracy of the key output models was very high for the entire range of the data. Sabine Conclusions UL TRAMAX SPO proved to be extremely effective in both lowering NOx emissions and, through improved efficiency, minimizing the costs of operation associated with evolving emissions goals. It was demonstrated that Sabine Unit 3 could meet much lower NOx levels at full load (as low as 0.148 Ibs/MBtu) than was previously believed. More important, it demonstrated that this could be done without significant boiler efficiency penalties. As a result, Entergy is able to move forward with confidence in its NOx RACT plant-wide averaging plan and is assured that it will not be necessary to carry out other, more expensive contingency plans. CASE 2 - DETROIT EDISON'S RIVER ROUGE PLANT River Rouge Background Another large utility that is utilizing SPO as a tool for lowering NOx emissions and optimizing boiler performance is Detroit Edison. The company has applied SPO to tune two coal-fired units at its River Rouge Plant in order to evaluate the technology for possible system-wide usage6 • Tuning will be used first as a least-cost option to reduce NOx with only operator adjustments, show the true capability of the units and define the margins available when the Phase II rules become effective in 2000. River Rouge Unit 3 utilizes a Foster Wheeler, twin-furnace, front wall-fired boiler that began commercial service in 1958. The fuel is a blend of Western and Eastern Coals, supplemented by blast furnace and coke oven gas. The unit is currently rated at 270 net MW. Detroit Edison conducted an optimization (or tuning) of Unit 3 to fulfill three requirements: reduction of NOx emissions, preservation or improvement of boiler performance, and maintenance of key operating parameters. Game Plan Development The game plan for River Rouge Unit 3 tuning is shown in Figure 5. Controlled inputs included lower and middle burner level mill bias; burner tertiary air damper position; burner secondary air register positions; BFG/COG (Blast Furnace, Coke Oven Gases) secondary air (windbox supply) damper position; and excess oxygen. Uncontrolled inputs were gas fuels, gross load and Low Sulfur Western coal blend. Outputs were NOx emissions; percent unburned carbon in the fly ash (UBC); flue gas carbon monoxide; steam temperature; dry gas loss; percent opacity; furnace exit gas temperature (FEGT); air heater temperatures; windbox pressures; percent of excess oxygen; boiler performance loss (BPL); and "Pain." The last-named output was a function which included the yearly cost attributed to boiler performance losses and NOx emissions. 5 |