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Show INTRODUCTION Currently in the United States there are approximately 40 gigawatts of oil- and gas-fired electrical capacity and SO gigawatts of coal-fired capacity that are being generated by plants that are over 30 years old. By the year 2000, there will be about 800 fossil-fired plants over 40 years old. As each of these existing generation plants gets older, decisions have to be made whether to retire or maintain the units. There are three major issues that arise when making decisions about older generating units. The first is that plant maintenance programs need to be much more aggressive to arrest the degradation of the generating plants. This higher level on maintenance implies a much higher maintenance cost as the plant ages. Often a large capital improvement program (life-extension program), especially for the boiler, must be initiated to continue plant operation. The second factor that must be considered is that the older generating plants are operating at much lower average efficiencies than their original design levels. This makes these plants noncompetitive with newer generating units. Lastly, these older generating plants are unable to meet current pollution requirements, and future emission standards will become increasingly more stringent, perhaps prohibiting the operation of many of these older units unless a clean coal repowering technology is implemented. Aggregate electrical demand and the current low level of new construction dictate that the majority of these older generating plants will have to be maintained rather than retired. A plant life-extension program alone will usually not be enough to continue plant operation because of the need to meet emission control requirements. Coal-fired repowering options with simultaneous NOx and SOx emission control are needed. A review of currently available coal-fired repowering technologies with simultaneous NOx and SOx control reveals that economical options do not exist. This is particularly true for small generating units in the SO-to-2S0-MW range. At first look, some of the coal-fired repowering technologies appear to have promise, but problems with space limitations, higher-than-forecasted emission levels, and the economic unattractiveness of these technologies for small generating units reveal that these existing technologies are not suited to the majority of the potential repowering candidates. Therefore, a new coal-fired repowering technology is needed. 2 |