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Show Tangential Firing System 2000 (TFS 2000™ System) Development Program Overview The major goal for the TFS 2000™ system development program is a tangential-firing technology to meet 0.10 to 0.15 lb/106 Btu N O x emissions level on Eastern U.S. bituminous coals, to make pulverized coal firing competitive on an emissions basis with other new coal-fired boiler technology options, such as fluidized bed combustors and IGCC. The N O x emission target is to be achieved through combustion techniques only, while maintaining carbon-in-ash at less than 5%, and C O emissions at less than 50 ppm. A laboratory development plan was implemented based on four (4) major elements: 1) coal pulverization and classification, 2) fuel admission and combustion near the coal nozzle tip, 3) lower furnace combustion, and 4) upper furnace combustion (between the main windbox and the furnace arch). Optimization of these individual elements was followed by a systems integration of these elements into the TFS 2000™ system. TFS 2000™ System Design Features The TFS 2000™ system is designed for minimum total emissions. Techniques employed to reduce N O x formation, such as sub-stoichiometric primary zone combustion, staging of fuel and air mixing, reduced excess air, and lower heat release rates, are all aimed at controlling the combustion rate and reducing peak flame temperatures. Since these conditions may increase the potential for CO, hydrocarbons, and increased unburned carbon emissions, a balance among these opposing factors is achieved through an integrated firing system (TFS 2000™ system) that combines finer coal pulverization with advanced fuel admission assemblies and in-furnace air staging utilizing multiple air injection levels. This new tangential firing system incorporates the following design features (Figure • ABB C-E's HP series pulverizer with integral Dynamic Classifier (Figure 5). The Dynamic Classifier is designed to produce coal fineness levels of approximately 0% on the 50-mesh sieve, 1.5% on the 100-mesh sieve, and more than 8 5 % passing through the 200-mesh sieve. Rotating classifier vanes impart centrifugal forces onto the coal particles as they are transported through the classifier by the air stream. The balance of the forces created by the air stream and the rotating classifier vanes separates the large particles from the small particles. Small particles exit from the classifier, while larger particles are retained for further pulverization. The primary need for finer coal is to minimize combustible losses (unburned carbon) caused by the staged combustion process for N O x control. Finer coal can result in close ignition at the coal nozzle tip discharge, enhancing fuel-bound nitrogen conversion and its subsequent reduction to N 2 under staged conditions. Secondary 5 11-10 |