Applying the direct quadrature method of moments to improve multiphase FCC riser reactor simulation Abhishek Dutta a , Denis Constales a,b , Geraldine J. Heynderickx a,n a Laboratorium voor Chemische Technologie, Ghent University, Krijgslaan 281, Blok S5, B-9000 Gent, Belgium b Vakgroep Wiskundige Analyse, Ghent University, Galglaan 2, Blok S22, B-9000 Gent, Belgium HIGHLIGHTS c Riser modeling using Direct Quadrature Method of Moments for catalyst particles. c Coupled with 12-lump FCC heterogeneous kinetics. c Using reliable drag closure model accounting for polydispersity. c Results are closer to data from FCC industrial plant in literature. article info Article history: Received 15 July 2011 Received in revised form 15 March 2012 Accepted 19 April 2012 Available online 7 May 2012 Keywords: Petroleum Multiphase reactions Population balance Catalysis DQMOM FCC riser abstract The hydrodynamic behavior of dispersed gas–solid flow is simulated for an industrial-scale Fluid Catalytic Cracking (FCC) riser using the multi-fluid approach, with complementary information from the Kinetic Theory of Granular Flow (KTGF) for the transport coefficients of the solid phase. A continuous Particle Diameter Distribution (PDD) is considered for the solid phase catalyst. The three-dimensional gas–solid flow is considered to be non-isothermal and turbulent. The hydrody- namics of the riser reactor is coupled to a 12-lump FCC kinetic model to predict the influence of a polydisperse distribution on gas–solid reactive flow. The kinetic model involves lumped species consisting of paraffins, naphthenes, aromatic rings, and aromatic substituent groups in medium and heavy fuel oil fractions and includes the effect of aromatic ring adsorption and catalyst deactivation due to coke formation. In this study, a Computational Fluid Dynamics (CFD) model using the Eulerian– Eulerian multi-fluid approach and a Population Balance Model (PBM) are coupled. The hydrodynamic equations are solved by means of a finite volume method, while the population balance equations are solved using the Direct Quadrature Method of Moments (DQMOM). The moments of the solids phase velocity are modeled using classical kinetic theory, while the moments of the PDD are described using quadrature weights and abscissas. To account for the catalyst PDD, three different approaches namely simple, surface-averaged and volume-averaged coupling have been attempted. The latter two approaches, assuming surface and volumetric reaction kinetics respectively, predict with a good precision the yields of the different product families obtained in an industrial FCC unit showing a slight improvement from a conventional heterogeneous reactor model with a monodispersed distribution. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Fluid Catalytic Cracking (FCC) plays a key role in an integrated refinery as it is a primary conversion process (Sadeghbeigi, 1995). Since its introduction in the 1940s, the FCC technology has been subjected to higher product quality demands, unstable economics and stricter environmental regulations. The FCC process evolves by contacting the vaporized feed with a solid zeolite catalyst once the preheated (330–370 1C) liquid feedstock is injected with steam through feed nozzles near the bottom of the riser. The hot catalyst (650–730 1C), regenerated by combustion of the coke on the catalyst, is circulated from the FCC regenerator via a standpipe to the bottom of the riser (see Fig. 1). The feed vaporizes almost instantaneously when it comes into contact with the hot, regenerated catalyst. As the gas and the catalyst flow upward in the riser, the gas is cracked into lighter hydro- carbons (gasoline and light gases) and coke. The expanding volume of the light vapors that are formed during reaction is the main driving force that enables the catalyst particles to move upward in the riser (Das et al., 2003). The deactivated catalyst is Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/ces Chemical Engineering Science 0009-2509/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ces.2012.04.036 n Corresponding author. Tel.: þ32 9 264 96 56; fax: þ32 9 264 49 99. E-mail address: geraldine.heynderickx@ugent.be (G.J. Heynderickx). Chemical Engineering Science 83 (2012) 93–109