3936 r2010 American Chemical Society pubs.acs.org/EF Energy Fuels 2010, 24, 3936–3941 : DOI:10.1021/ef100443s Published on Web 06/15/2010 Design and Test of a Selective Noncatalytic Reduction (SNCR) System for Full-Scale Refinery CO Boilers To Achieve High NO x Removal Wei Zhou,* ,† Antonio Marquez, † David Moyeda, † Santosh Nareddy, † Jennifer Frato, † Guanghui Yu, † Sigbjørn Knarvik, ‡ and Vidar Frøseth ‡ † General Electric Energy, 1831 Carnegie Avenue, Santa Ana, California 92705, and ‡ Statoil ASA, Mongstad Refinery, N-5955 Mongstad, Norway Received April 8, 2010. Revised Manuscript Received May 29, 2010 Selective noncatalytic reduction technology (SNCR) is an effective and economical method of reducing NO x emissions from a wide range of industrial combustion systems. It is widely known that the SNCR process is primarily effective in a narrow temperature window, around 900-1000 °C, and that high CO concentrations can both shift the temperature window and limit its effectiveness. While the application of SNCR on a utility boiler is challenging because of a number of factors that can have negative impacts on SNCR NO x reduction performance, the implementation of SNCR technology on an industrial or refinery boiler has unique challenges intrinsic to these boiler designs and fuels fired. This paper describes the design and test of SNCR technology on two refinery CO boilers. The work presented consisted of (1) baseline testing, (2) process analysis, (3) computational fluid dynamics (CFD) simulations, and (4) optimization testing. A three-dimensional full-scale CFD model was constructed for the boiler and was calibrated using baseline test data to simulate the flow characteristics, temperature profile, and oxygen/combustibles distribution of the boiler. The CFD model was also used to design and optimize a reagent injection system that resulted in fast and effective distribution of the reagent in the flue gas of the boiler. The CFD model, which incorporates a reduced SNCR chemistry model, was further applied to predict NO x reduction efficiency and ammonia slip. After installation and commissioning of the SNCR system, a series of parametric optimization tests were performed on both units. The final performance tests showed that the application of SNCR technology could reduce NO x emissions by at least 50%, with less than 5 ppm of ammonia slip, at a nitrogen stichiometric ratio (NSR) of 1.5. The test results are shown in the paper for a comparison to the model predictions made during the design phase. 1. Introduction Selective noncatalytic reduction (SNCR) technology has been applied to utility boilers, waste incinerators, and other stationary combustion systems for NO x control. 1-4 It is a flue gas treatment process, in which a nitrogen-containing agent, such as ammonia (NH 3 ) or urea [CO(NH 2 ) 2 ], is injected into the combustion gases to react with and reduce NO x formed during the combustion process. 5 At the proper temperature window, NH 2 , NH, and N, generated from the decomposition of the injected reagent, react directly with NO to form N 2 . Although the optimum process temperature depends upon the agent and furnace quench rate, the accepted window for SNCR application is generally at temperatures between 900 and 1000 °C. The challenges for a SNCR retrofit of a utility boiler include (1) large temperature gradient and, therefore, short residence time of the reagent in the SNCR window, (2) dynamic and unsteady boiler conditions, (3) a wide range of loads that requires multiple layers of injections, (4) difficult to achieve good mixing between the reagent and the flue gas, especially at the center of the furnace, and (5) high flue gas temperature, forcing injectors to be placed near or between the tube bundles. A refinery or industrial boiler on the other hand typically has a process condition that favors SNCR techno- logy. For example, a CO boiler often runs at a relatively steady load, and its flue gas temperature at the exit of the combus- tion chamber is usually closely controlled in the range of 860-1050 °C. Another example is for application on process heaters. The process heater often has low CO emissions, and its flue gas temperature is around 1000 °C. However, to design a system that can achieve optimal NO x reduction performance, careful use of design tools is needed to identify the best loca- tion for reagent injection, to maximize residence time and *To whom correspondence should be addressed. Telephone: 949-794- 2628. E-mail: wei.zhou@ge.com. (1) United States Environmental Protection Agency (U.S. EPA). EPA 171-R-92-003. The use of SNCR as BACT for NO x control in boilers and municipal solid waste incinerators, http://nepis.epa.gov. (2) Nguyen, Q. H.; Zhou, W.; Moyeda, D. K.; Payne, R.; Suter, R. A successful SNCR design with CFD applications in a gas fired CO boiler. AIChE Annual Meeting, Cincinnati, OH, Nov 4, 2005, http://aiche. confex.com/aiche/2005/preliminaryprogram/abstract_32081.htm. (3) Himes, R.; Quartucy, G.; Muzio, L.; Cremer, M.; Sun, W. Evaluation of SNCR trim on a 185 MW tangential design coal-fired utility boiler. In Proceedings of 2002 DOE Conference on Selective Catalytic and Non-catalytic Reduction for NO x Control, Pittsburgh, PA, May 2002. (4) Horton, J.; Linero, A.; Miller, F. M. Use of SNCR to control emissions of oxides of nitrogen from cement plants. Cement Industry Technical Conference, Phoenix, AZ, 2006; Conference Record. Institute of Electrical and Electronics Engineers (IEEE): New York, p 29. (5) Lyon, R. K. Method for the reduction of the concentration of NO in combustion effluents using ammonia. U.S. Patent 3,900,554, 1975. (6) Nguyen, T. D. B.; Yang, T.-H.; Lim, Y.-I.; Eom, W.-H.; Kim, S.-J.; Yoo, K.-S. Application of urea-based SNCR to a municipal inci- nerator: On-site test and CFD simulation. Chem. Eng. J. 2009, 152 (1), 36–43.