Chemical Engineering Journal 152 (2009) 36–43 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej Application of urea-based SNCR to a municipal incinerator: On-site test and CFD simulation Thanh D.B. Nguyen a , Tae-Ho Kang a , Young-Il Lim a,∗ , Won-Hyeon Eom b , Seong-Joon Kim b , Kyung-Seun Yoo b a Lab. FACS, RCCT, Department of Chemical Engineering, Hankyong National University, Gyonggi-do, Anseong-si, Jungangno 167, 456-749, Republic of Korea b Department of Environmental Engineering, Kwangwoon University Seoul, Nowon-gu, Wolgye-dong 447-1, 139-701, Republic of Korea article info Article history: Received 14 October 2008 Received in revised form 11 March 2009 Accepted 18 March 2009 Keywords: NOx reduction Selective non-catalytic reduction (SNCR) Computational fluid dynamics (CFD) Urea solution Nonuniform droplet size Incinerator abstract NO x controlling in a municipal solid waste incinerator by selective non-catalytic reduction (SNCR) using urea–water solution is studied by means of computational fluid dynamics (CFD) simulation, which is validated with on-site experiments. A three-dimensional turbulent reacting flow CFD model including the reduced chemical kinetics and the reagent droplet phase is developed to predict the performance of the SNCR process installed in the incinerator. At normalized stoichiometric ratio (NSR)=1.8, 70% NO (nitrogen oxide) reduction is obtained from on-site experiments, while 66% NO reduction is from the CFD simulation with the nonuniform droplet size. NH 3 slip obtained from the CFD simulation is in reasonable agreement with the in-situ experiment. The effect of the droplet size distribution on the nitrogen oxide reduction efficiency is examined on CFD simulation results. Since the NO concentration at the SNCR exit is more dispersed in the nonuniform droplet size than in the uniform one, the nonuniform droplet size enhances mixing with the flue gas and increases the NO reduction efficiency. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Environmental protection and stringent emission limits both require a significant reduction of nitrogen oxides (NO x ) emissions from industrial boilers as well as waste incineration plants. In recent years, the selective non-catalytic reduction (SNCR) technology, a flue gas treatment method for NO x emission control, has achieved commercial applications to stationary combustion sources [1]. The technology is attractive due to its simplicity, catalyst-free system, ease of installation on existing plants, applicability to all type of stationary-fired equipments, and lower capital cost [2]. In SNCR the reagent is employed at high temperatures by injection into the combustion chamber. Ammonia (NH 3 ) and urea (CO(NH 2 ) 2 ) are common reducing reagents. In waste incineration plants, the reduction of NO x may range from 60% to 80% under the relevant conditions [3]. Although the technology is considered as simple to install and operate, it has a quite complex chemistry and requires fine oper- ating conditions. In additions, its efficiency of NO x reduction is specific to each application having different design parameters and operating conditions. The performance of the SNCR process is strongly influenced by several factors including (1) flue gas tem- ∗ Corresponding author. Tel.: +82 31 670 5207; fax: +82 31 670 5445. E-mail address: limyi@hknu.ac.kr (Y.-I. Lim). perature at the reagent injection zone, (2) flue gas residence time in the relevant temperature range, (3) reagent/NO x molar ratio (or normalized stoichiometric ratio (NSR) = 2n urea /n NO , where n urea is the mole of urea in the urea solution and n NO is the mole of NO in the inlet flue gas), and (4) mixing conditions [1]. The optimum temper- ature is between 900 and 1000 ◦ C in general. With increase of NSR, the reduction efficiency rises up to NSR of about 2 and thereafter generally levels off [3]. Owing to the tightened emissions standards and the desire for the lower cost NO x emission control, improved computational tools are needed for SNCR design and optimization [4]. Moreover, sim- ulations of chemical process equipments, chemical reactors and a variety of industrial combustion devices using computational fluid dynamics (CFD) tools have gained increasing popularity [5]. CFD has been widely applied to aid the design of SNCR and NO x emission controlling systems at a full scale [6–10]. In spite of the advantages of computational tools, the imple- mentation of the detailed full chemical kinetics of SNCR [11] on CFD simulations for practical systems is prohibitive from the standpoint of both CPU time and memory. Thus, a reduced chemical kinetic mechanism is widely used [4,7,12–15]. In the present work, the reduced kinetic mechanism with a seven-step global chemistry is implemented on the three- dimensional (3D) turbulent reacting flow CFD model to predict the urea-based SNCR process performance in a municipal solid waste (MSW) incinerator. These kinetics parameters [15] are identified on 1385-8947/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2009.03.025