Simulation-Based Optimization of Monolith Catalytic Reactors for the Reduction of NOx Emission

ANA MARISA ARIAS; MIGUEL MUSSATI,; NICOLÁS J. SCENNA; TOMASIC VESNA ; GOMZI ZORAN ; SERGIO F. MUSSATI

Buenos Aires

Congreso; CAIQ2015 -VIII Congreso Argentino de lngenieria Química y las 3JASP - Terceras Jornadas Argentinas de Seguridad de Procesos.; 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 modeling 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 of monolith catalytic reactors for the reduction of NOx and a simulation-based optimization method is employed to determine the optimal reactor dimensions (diameter and length) and operating conditions in order to satisfy fixed levels of NOx conversion at minimum total annual cost. The total model equations describing the behavior of the reactor are solved using gPROMS (gPROMS, 2001), which is a software package for process modeling and simulation with both discrete and continuous as well as lumped and distributed characteristics. Several case studies are presented to discuss the obtained results in detail.