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Show System Process Design The project was initiated by an exchange of boiler design information among the U.S., Russian, and Ukrainian teams. Meetings were held in the U.S., Moscow, and at Ladyzhin, Ukraine, in order to facilitate the transfer of information. Reburn system process design was then initiated based on the following overall process objectives: 1. Meet key design criteria for effective NOx reduction while minimizing any impact on normal boiler operation. 2. Incorporate operational flexibility within the design to permit optimized host unit performance. The process by which the preliminary design was established by the U.S. team was previously reported6. A brief summary of the process follows. Key design criteria commensurate with the overall design objectives for the reburn system were initially established. The criteria consist of theoretical criteria for effective N O x reduction, obtained through the open literature, and practical, commercial considerations for reburn system design, installation, and operation. With these criteria in mind, as well as the Ukrainian utility's requirements that the reburn system not adversely affect slag tapping, not increase tube metal temperatures beyond design limits, and not affect general slagging /fouling characteristics, A B B Power Plant Laboratories initiated the preliminary design by performing mass balance and combustion calculations on the overall process. Existing process flows were used in this calculation, along with actual coal chemical analysis, an estimate of flue gas recirculation (FGR) mass flow necessary for the fuel injectors (natural gas used as reburn fuel, F G R as a transport m e d i u m to enhance mixing), furnace dimensions, and Russian/Ukrainian-supplied furnace gas temperature information. A proprietary computer code was employed to calculate stoichiometric ratios and gas residence times in boiler zone 1 (the furnace bottom to the reburn zone start or main burner/primary zone), zone 2 (the reburn fuel injection position to the burnout air injection position or reburn zone), and zone 3 (the burnout air injection position to the horizontal furnace outlet plane, or burnout zone). Estimates for the reburn fuel and burnout air injection position (elevation) were input into the code and then iteratively adjusted to achieve reburn/burnout zone stoichiometries and furnace gas residence times consistent with the key design criteria. Physical Flow Modeling Isothermal flow modeling studies were conducted to optimize the number, locations, configuration, and operating parameters for the reburn fuel and burnout air injector system. Baseline furnace aerodynamics were evaluated as well as the performance of a number of candidate reburn system configurations. Total mass flow rates for the 5 |