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Show cost tool to gain improvements in emissions control and thermal performance prior to decisions on capital-intensive solutions3 • This empirical method of optimization can determine the true boiler capabilities and help delay, or even avoid, expensive retrofits or repowering. It can serve as a least-cost means of attaining the right degree of compliance with current and future phases of CAAA4. Tuning ensures a staged strategy to stay ahead of emissions regulations, but not so far ahead as to cause regret for taking actions that ultimately are not mandated or warranted. In this paper we will examine three different applications of SPO technology to fossilfired boilers at Entergy's Sabine Station, Detroit Edison's River Rouge Plant and Illinois Power's Hennepin Station. These applications differ in fuel, design, objectives and manner of implementation. One type of boiler is fired by natural gas, one by a coal blend supplemented by blast furnace and coke oven gases, and the third by pulverized coal only. One application involves integration with a distributed control system to provide a continuous, on-line operator advisory capability while another is a one-time optimization to determine boiler unit capabilities. CASE 1 - ENTERGY'S SABINE STATION Sabine Background Sabine Station, owned and operated by the Entergy Corporation, is a 2000 MW plant consisting of five separate natural gas-fired units located in the Beaumont-Port Arthur, Texas, moderate ozone non-attainment area. Entergy has developed a compliance strategy to address pending NOx Reasonable Available Control Technology (RACT) requirements for this area. The RACT rule allows plant-wide averaging to meet a combined heat input weighted average of 0.2 Ibs/MBtu on a rolling, 30-day basis. Entergy determined that Sabine Station Unit 3, a 420 MW net, CE tangential-fired boiler, was a critical unit in the ability of the plant to meet its NOx RACT limit and avoid the installation of additional NOx controls at other units. The Entergy strategy is to avoid installation of new control technology by overcontrolling certain key units through optimization of existing equipment. Improvement of boiler performance was also deemed critical not only to Entergy's compliance strategy, but also to the utility's goal of enhancing efficiency in order to produce electricity at the lowest cost. Through a Tailored Collaboration with EPRI, Entergy used boiler tuning with SPO as a first step in realizing these goals5 • The primary objective of the project was to reduce NOx emissions as much as possible at full and low loads, without adverse effect on heat rate and other key operating and emission parameters. The secondary objective was to reduce heat rate while constraining NOx emissions below RACT compliance targets. Combustion Tuning with SPO Optimization with SPO begins with the development of a game plan or process formulation. Based on the experience of the Sabine Station staff, the game plan for Unit 3 included the key input and output parameters, operating constraints and optimization goals summarized in Figure 2. The eventual set of controlled inputs consisted of the O2 setpoint, burner tilts, windbox to furnace differential pressure, main dampers and gas recirculation fan loads. An uncontrolled input was burner gas pressure. Constrained outputs were CO, reheat steam temperatures, reheat balance, superheat steam temperatures, superheat balance, O2, air heater gas inlet temperature 3 |