Selective Catalytic Reduction (SCR) Technology for the Control of Nitrogen Oxide Emissions from Coal-Fired Boilers

The Clean Coal Technology Demonstration Program (CCTDP) is a government and industry co-funded effort to demonstrate a new generation of innovative coal utilization processes in a series of facilities built across the country. These projects are carried out on a commercial scale to prove technical feasibility and provide information for future applications. The goal of the CCTDP is to furnish the marketplace with a number of advanced, more efficient coal-based technologies that meet strict environmental standards. Use of these technologies is intended to minimize the economic and environmental barriers that limit the full utilization of coal. To achieve this goal, beginning in 1985, a multi-phased effort consisting of five separate solicitations was administered by the U.S. Department of Energy (DOE) through its National Energy Technology Laboratory (NETL). Projects selected through these solicitations have demonstrated technology options with the potential to meet the needs of energy markets while satisfying relevant environmental requirements. Part of this program is the demonstration of technologies designed to reduce emissions of oxides of nitrogen (NO x) from existing coal-fired utility boilers. NO x is an acid rain precursor and a contributor to the formation of ground-level atmospheric ozone, which is a health hazard and is also related to smog formation. NO x emissions are regulated under the provisions of the Clean Air Act Amendments (CAAA) of 1990. In 1995, a CCTDP project was concluded that demonstrated selective catalytic reduction (SCR) technology for the control of NO x emissions from high-sulfur, coal-fired boilers. The project was conducted by Southern Company Services, Inc., who served as a co-funder and as the host at Gulf Power Company's Plant Crist. The SCR process consists of injecting ammonia (NH 3) into boiler flue gas and passing the flue gas through a catalyst bed where the NO x and NH 3 react to form nitrogen and water vapor. The results of the CCTDP project confirmed the applicability of SCR for U.S. coal-fired power plants. In part as a result of the success of this project, a significant number of commercial SCR units have been installed and are operating successfully in the United States. By 2007, the total installed SCR capacity on U.S. coal-fired units will number about 200, representing about 100,000 MWe of electric generating capacity. This report summarizes the status of SCR technology.