Reducing NO x emissions in tangentially-fired boilers-a new approach

Abstract

Introduction Power plant owners and operators, especially those with coalfired capacity, are facing both significant opportunities and challenges. The move to deregulate the U.S. power industry presents an opportunity for existing coal-fired power plants because of their low fuel cost, and many are forecasting near-term growth of this type of generation. The associated open market, however, will force all power generators to control capital expenditures, reduce operating and maintenance (O&M) costs, and maximize overall plant efficiency to remain competitive. At the same time, plant operators and owners are facing the need to meet significantly tighter nitrogen oxides (NOx) regulations as a result of the Clean Air Act Amendments (CAAA) of 1990. Lower NOx emissions require both increased capital and operating costs that produce a negative impact on overall plant efficiency. The winners in this race are those that drive costs down by selecting technologies that meet the emissions requirements at minimal capital and operating costs. Most technologies apply some type of air staging, for the reduction of NOx emissions as required by the Title IV Phases I and II of the CAAA with reasonable operating and capital costs. The anticipated further reduction in NOx emissions levels as a result of Title I (ozone non-attainment) requirements further increases the pressure on the utility boiler owners and operators. Depending on where the final regulations are set, the use of more costly technologies such as Selective Catalytic Reduction (SCR) may be required. At Duke Power Co., a building block approach has been applied to the NOx strategy. The Duke project manager for his effort also called upon and applied his personal religious convictions and beliefs to develop the best solution at the least cost. In anticipation of more stringent Title I regulations, Duke Power and Babcock & Wilcox (B&W) reworked the tangentially-fired Marshall Unit 3 with a low NOx combustion system that will maximize NOx reductions thereby minimizing the costs of future technology for NOx control.