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Show LIMESTONE FEEDER COAL FEEDE PULVERIZER RECYCLE SOLIDS TANK FIGURE 3 LEBS COMMERCIAL GENERATING UNIT CONCEPT SELECTION STACK C1S7ll1d6O The NOx subsystem includes fuel preparation and delivery, air preheating and delivery, burners, air/fuel injectors, furnace, and controls hardware and software. Some of these areas are also covered by the Boiler and Controls & Sensors subsystems, therefore, only the burners, furnace, and the combustion system strategies were focused on by the NOx subsystem. The initial step in Phase I was the identification of candidate concepts for each component of the subsystem. The initial screening considered NOx reduction potential, turndown ratio, stability over a wide range of air/fuel ratios, and proven commercial performance. From this screening, three burner types, four major furnace configurations, and three combustion system strategies were selected for further evaluation. Preliminary design concepts were developed for each combination strategy and selected furnace configuration. The preliminary design concepts included burner sizing and arrangement, characteristic furnace dimensions, and thermal histories. The information developed in the preliminary design was used to quantify an expected NOx emission and implementation risk for each design concept. The design concepts were then evaluated using a K-T analysis with relative NOx emission, cost, and operational constraints as desirable criteria. This process is depicted in Figure 4. The results of this analysis showed that a venturi furnace configuration with advanced staged combustion and advanced 10w-NOx 4 |