Low-NO_x burners and other combustion modifications have been the most often used strategy for satisfying Clean Air Act Amendment Phase I limits. Although many regard this technology as "plug and play" equipment, field experience has often shown otherwise. Plants that have implemented combustion modifications often report difficulties in two areas: unburned carbon in flyash and waterwall corrosion, the focus of this discussion. Approximately ten percent of Phase I units are experiencing accelerated waterwall tube wastage associated with low-NO_x firing. The extent of the problem varies from noticeable, but manageable, to unacceptably frequent forced outages. As availability has a major impact on the cost of power produced by a particular plant, the real cost of low-NO_x firing systems may be significantly greater than the equipment/installation cost.
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