An evaluation of micronized coal reburning for nitrogen oxide emissions reduction in pulverized coal-fired electric utility boilers

Recent increases in the prices of imported fuels and increases in the cost of natural gas have underscored the need to consider other sources of energy for electric production in the United States. Our most abundant fuel source is coal, however the use of coal brings with it a set of environmental problems. This dissertation presents an investigation into the use of micronized coal reburning. This technology may provide a cost-effective solution to the requirements to reduce NO_x emissions from pulverized coal-fired electric generating stations.; This research effort evaluated the use of micronized coal as a reburning fuel to lower nitrogen oxide emissions from coal-fired boilers. The research effort included: (1) an investigation of all available literature on the subject, (2) planning and supervision of a number of baseline and parametric tests on a full-scale coal fired utility boiler. The testing was carried out on the former NYSEG generating unit, Milliken 1. Milliken Unit 1 is a 150 MW coal-fired electric utility boiler located in Lansing, NY on the eastern shore of Cayuga Lake, (3) development of a model to predict NO_x emissions from a coal-fired boiler, and (4) completion of a conceptual design for a micronized coal reburning system.; The original plan of the research effort was to include a full-scale micronized coal reburn installation and subsequent modeling and testing. However, in 1998 the deregulation of the electric utility industry in New York caused the focus of the dissertation to be narrowed. The test site, Milliken Station was sold to another entity, and the installation of the micronized coal reburn system was cancelled.; The following conclusions were drawn from the research: (1) Testing showed that nitrogen oxide production was significantly influenced by changes in controllable boiler operating parameters. (2) The predictive model for baseline nitrogen oxide production was fairly accurate in estimating NO_x emissions. The model had an average error of 10.14%, with about half of the 27 model runs being within 10% accuracy, and only two runs having greater than a 20% error. (3) The conceptual design shows that in most cases, the physical characteristics of existing coal fired boilers, and existing operating methods will allow for installation of micronized coal reburn systems. (4) An estimate of micronized coal reburning performance was made. It is estimated from a review of existing bench and pilot scale tests, modeling, and natural gas reburn projects that nitrogen oxide emissions can be reduced by about 60%, to a level of approximately 0.128 pounds per mmbtu of heat input. (5) Given impending, more stringent NO_x regulations, and the high cost of natural gas, which has been demonstrated as a successful reburn fuel, micronized coal reburning is a cost effective alternative to current methods of NO _x control.