Aqueous urea is converted into ammonia through hydrolysis downstream of the injection nozzle. In the presence of the highly reactive, homogeneous, extruded SINOx (SCR) diesel catalysts, the nitrogen oxides (NOx) react with the ammonia
(NH3) to yield nitrogen (N2) and water vapor (H2O). The operating temperature range is approximately 300–1020F. An oxidation catalyst is not required if an SCR diesel catalyst is used, because the fuel-efficient heavy-duty diesel engines practically produce no CO and very little VOC/HC and PM, which are further reduced by 80–90% and 20–30%, respectively. Oxidation catalysts are even unde- sirable if sulfur-containing fuel is used.
The SINOx system is controlled automatically by a programmable micropro- cessor-based process logic control system. Active monitoring or supervision of the system by the operator is not required.
Summary on a Urea SCR Application in a Coal-Burning Utility Operation, American Electric Power Gavin Plant at Cheshire, Ohio Rated 2 X 1300 MW
American Electric power (AEP), an international energy company based in Colum- bus, OH is capable of producing 38,000 MW electricity in 11 U.S. states and has a customer base of more than 4.8 million. AEP and other power generators in the Midwest and Southeast are required by court order to reduce their NOxemission
by May 2003. AEP’s Gavin Plant has two 1300-MW generating units and is the largest utility station in Ohio This AEP Urea SCR project is designed to reduce NOxby approximately 70% to 0.15 lbs./pBTU of the coal-burning plant’s utility
boilers at a cost of US$ 175 million. This project uses urea rather than anhydrous or aqueous ammonia as the reducing agent to overcome local safety concerns about the transport, handling, and storage of ammonia. (See Fig. 40.)
Acknowledgments
The author would like to thank Siemens powergeneration’s KPW Group, Redwitz, Germany and Alpharetta, GA (USA) for supporting this project. The author is especially thankful to Dr. Juergen Zuerbig, head of Siemens’ SCR Business world-
wide and Dr. Raimund Mueller,* Head of the U.S. SCR Business and their staff for the support received and for the permission to incorporate Siemens material, used in prior papers and public presentations for this project. Without sharing their inside information about the European advancements in the SCR technology, in particular in mobile SINOx diesel catalyst applications in recent years, this project would not have been possible.
Also, the author would like to thank EESI/Steuler for the support received and the permission to use material from public and internal documentation. The author is especially thankful to Nick Detor, Engineering and Project Manager of EES Inc., Cerritos, CA and Hans J. Wagner, Senior Manager of Steuler’s equipment Division, Hoehr–Grenzhausen, Germany who provided valuable information about some CER-NOxzeolite SCR catalyst applications.
Furthermore, the author would also like to thank Dr. Ray Anthony, professor and head of the Chemical Engineering Department, Texas A&M University and his staff for their valuable guidance and editing effort. Finally, the author would like to thank the many professionals in the air pollution control community in the United States and Europe, with whom he has been associated over the years. The information shared privately, at conferences, and while serving with the author on committees in California, such as the Scientific Review Committee on Best Avail- able Control Technology (BACT) at SCAQMD, on IC engines at Cal. ARB, and at joined projects at the University of California, was most helpful.
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