SIMULATION-BASED OPTIMIZATION OF MONOLITH CATALYTIC REACTORS FOR THE REDUCTION OF NOx EMISSION

ANA M. ARIAS; NICOLÁS J. SCENNA; MIGUEL C. MUSSATI; SERGIO F. MUSSATI; VESNA TOMASIC; ZORAN GOMZI

Buenos Aires

Congreso; VIII Congreso Argentino de Ingeniería Química; 2015

Asociación Argentina de Ingenieros Químicos

Monolith reactors were widely applied to the automobile industry to reduce emissions of undesired products from the exhaust gases. In the last time, monoliths are increasingly under development and evaluation for many new reactor applications. Compared to the traditional catalysts used for gas phase reactions, monolith reactors are preferred to the exhaust gas treatment, because of their high conversion rate, reaction performance and selectivity and elimination of hot-spot [Chen et al. (2008)]. The advantages of monolith converters over the conventional reactors with particular focus on the integral approach to the catalyst and reactor design are clearly pointed out in Tomasic and Jovic (2006). During the last years many research activities in NOx control technologies have been done in different lines from experimental studies at laboratory scale [Tomasic and Gomzi (2004), Rico-Perez et al. (2013), Lumpiañez et al. (2013), Kang et al. (2014)] to the development and implementation of mathematical models in computers [Ghadrdan and Mehdizadeh (2008), Jirát et al. (1999), Shakya et al. (2014), Gundlapally and Balakotaiah (2013), Yun and Kim (2013), Kim et al. (2012), Zukerman et al. (2009), Stepánek et al. (2011)].Simulations and development of mathematical models can be effectively used to gain insights and identify trade-offs between the process variables which help to determine feasible and optimal process designs.Despite of the many publications dealing with the modelling and simulation of selective catalytic reduction (SCR) technology, the state of art reveals that there are only few articles addressing the optimization of SCR technologies for NOx emissions using mathematical programming approaches and detailed models [Tronci et al. (1999), Ramanathan et al. (2004), Kim and Kim (2007), Desmet et al. (2003), Kim et al. (2009), Chen and Tan (2012)]. In addition, it is also possible to conclude that there are no articles dealing with the use of robust optimization algorithms applied to the design and operation of catalytic NOx converters.In this paper, a detailed mathematical model to optimize monolith catalytic reactors for the reduction of NOx emission as well as an efficient solution strategy will be developed. The proposed model and the solution procedure should be robust enough in order to guarantee the convergence for any particular input data provided by users. Reactor dimensions (diameter and length) and operating conditions will be optimized simultaneously. The resulting PDAEs are converted to a set of nonlinear algebraic equations using finite difference approximation (FDM) and are implemented into the optimization environment GAMS (General Algebraic Modeling System). The objective function proposed to be maximized is the ratio between the NOx reduction and reactor volume and the optimal profile of temperature, NOx conversion, gas velocity as well as the reactor diameter and length are obtained simultaneously. In addition, the effect of each model parameter on the objective function is also investigated and discussed in detail. References- Chen J., Yang H., Wang N., Ring Z., Dabros T. ?Mathematical modeling of monolith catalysts and reactors for gas phase reactions?. Applied Catalysis A: General, Vol. 345, Issue 1 (2008), pp. 1-11.- Tomasic V., Jovic F. ?State-of-the-art in the monolithic catalysts/reactors?. Applied Catalysis A: General, 311 (2006), pp.112?121.- Tomasic V., Gomzi Z. ?Experimental and theoretical study of NO decomposition in a catalytic monolith reactor?. Chemical Engineering and Processing: Process Intensification, Vol. 43, Issue 6 (2004), pp. 765-774.- Rico-Pérez V., García-Cortés J.M., Salinas-Martínez de Lecea C., Bueno-López A. ?NOx reduction to N2 with commercial fuel in a real diesel engine exhaust using a dual bed of Pt/beta zeolite and RhOx/ceria monolith catalysts?. Chemical Engineering Science, 104 (2013), pp. 557-564.- Lupiáñez C., Guedea I., Bolea I., Díez L., Romeo L.M. ?Experimental study of SO2 and NOx emissions in fluidized bed oxy-fuel combustion?. Fuel Processing Technology 106 (2013), pp. 587?594.- Kang S.B., Han S.J., Nam I., Cho B.K., Kim C.H., Oh S.E. Detailed reaction kinetics for double-layered Pd/Rh bimetallic TWC monolith catalyst. Chemical Engineering Journal 241 (2014), pp. 273?287. - Ghadrdan M., Mehdizadeh H. ?Excerpt from the Proceedings of the COMSOL Conference 2008 Hannover?. https://www.comsol.de/papers/5325/download/Ghadrdan.pdf- Jirát J., ?těpánek F., Kubı́ček M., Marek M. ?Non-stationary operation of a system of catalytic monolithic reactors for selective NOx reduction?. Chemical Engineering Science 54 (1999), pp. 2609-2618.- Shakya B., Harold M., Balakotaiah V. ?Modeling and analysis of dual-layer NOx storage and reduction and selective catalytic reduction monolithic catalyst?. Chemical Engineering Journal, 237 (2014), pp. 109-122.- Gundlapally S., Balakotaiah V. ?Analysis of the effect of substrate material on the steady-state and transient performance of monolith reactors?. Chemical Engineering Science, Volume 92 (2013), pp. 198-210.- Yun B.K., Kim M.Y. ?Modeling the selective catalytic reduction of NOx by ammonia over a Vanadia-based catalyst from heavy duty diesel exhaust gases?. Applied Thermal Engineering, Vol. 50 Issue 1 (2013), pp. 152-158.- Kim M.K., Kim P.S., Kwon H.J., Nam I., Cho B.K., Oh S.H. ?Simulation of OHC/SCR process over Ag/Al2O3 catalyst for removingNOx from diesel engine?. Chemical Engineering Journal, 209 (2012), pp. 280-292.- Zukerman R., Vradman L., Herskowitz M., Liverts E., Liverts M., Massner A., Weibel M., Brilhac J.F., Blakeman P.G., Peace L.J.? ?Modeling and simulation of a smart catalytic converter combining NOx storage, ammonia production and SCR?. Chemical Engineering Journal, Volume 155, Issues 1?2, 1 December 2009, Pages 419-426.- Stěpánek J., Kocí P., Kubícek M., Plát F., Marek M. ?Spatially 3D simulation of a catalytic monolith by coupling of 1D channel model with CFD?.Computer Aided Chemical Engineering, 29 (2011), pp. 141-145.- Tronci, S., Baratti, R., Gavriilidis, A. Catalytic converter design for minimisation of cold-start emissions. Chemical Engineering Communications 173 (1999), pp. 53?77.- Ramanathan K., West D.W., Balakotaiah V. Optimal design of catalytic converters for minimizing cold-start emissions. Catalysis Today 98 (2004), pp. 357?373.- Kim Y.D., Kim W.S. ?Optimum design of an automotive catalytic converter for minimization of cold-start emissions using a micro genetic algorithm?. International Journal of Automotive Technology 8 (2007), pp. 563?573.- Desmet G., De Greef J., Verelst H., Baron G.V. Performance limits of isothermal packed bed and perforated monolithic bed reactors operated under laminar flow conditions. I. General optimization analysis. Chemical Engineering Science, Vol. 58, Issue 14 (2003), pp. 3187?3202.- Kim Y.D., Jeong S.J., Kim W.S. Optimal design of axial noble metal distribution for improving dual monolithic catalytic converter performance. Chemical Engineering Science 64 (2009), pp. 1373-1383.- Chen C.T., Tan W.L. Mathematical modeling, optimal design and control of an SCR reactor for NOx removal. Journal of the Taiwan Institute of Chemical Engineers, Vol. 43, Issue 3 (2012), pp. 409-419.