Journal of Multidisciplinary Engineering Science Studies (JMESS) ISSN: 2458-925X Vol. 2 Issue 10, October - 2016 www.jmess.org JMESSP13420213 985 CFD Simulation of Mixing Effect on a Continuous Stirred Tank Reactor 1 ٭ Ademola S. Olufemi Department of Chemical and Petroleum Engineering, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria e-mail:adestanford.olufemi@gmail.com 2 Oluwafemi O. Olayebi Department of Chemical Engineering, Federal University of Petroleum Resources, Effurun, Delta State, Nigeria e-mail:olayebi.oluwafemi@fupre.edu.ng 3 Iwekumo Wauton Department of Chemical and Petroleum Engineering, Niger Delta University, Wilberforce Island, Bayelsa State, Nigeria e-mail:tariebi2015@gmail.com 4 Ubong O. Ekanem Department of Chemical/Petrochemical Engineering, Akwa Ibom State University, Ikparenin, Akwa Ibom State, Nigeria e-mail:ubongekanem@aksu.edu.ng Abstract—The continuous Stirred tank reactor (CSTR) is a process equipment frequently used in the chemical, food and pharmaceutical engineering related industries. The effect of fluid flow and impeller characteristics on the mixing behavior of the reactor via computational fluid dynamics has been studied. ANSYS FLUENT12.0 CFD software is used for the simulation of a reactive flow process involving of a second order reaction. The rate of reaction is determined by the impeller speed and its position from the bottom of the reactor and therefore on the mixing behavior during the steady state process. The presented mixing behavior data were compared with the available experimental values in the open literature. The Impeller produces boundary conditions that are important aspects significantly enriching the mathematical representation of the primary source of motion in tanks. The results obtained from the simulation are compared with experimental values and were found to be in agreement with the experimental data in open literature. Keywords—CFD, CSTR, Ansys fluent, impeller, mixing I. Introduction Continuous stirred-tank reactors (CSTRs) are widely applied in the chemical, food, and pharmaceutical and related industries, for their good mixing ability, efficient heat and mass transfer and good scale-up characteristics [1, 2]. Mixing operation in CSTRs has been the subject of many investigations. Under non-premixed conditions, reactants must first come in contact and then undergo reaction. Physical phenomena/processes like diffusion, fluid pumping in the reactor and mechanical agitation control the mixing [3]. Mixing due to diffusion depends on concentration or temperature gradients [2]. In larger reactors, mixing by diffusion is not practically acceptable because of low rate of mixing. In most cases, the continuous reactors use mechanical agitation for mixing. Because of agitation, efficient mixing can occur irrespective of production capacity and viscosity of the fluid. The mechanical agitator provides better performance of CSTR, giving more conversion of reactant to produce [4]. The limitations in lumping processes are avoided by using the distributed parameter models, based on the actual hydrodynamics inside the reactor. A huge amount of information about these hydrodynamics cannot be obtained via experimentations [5]. The continuing development of commercial codes for computational fluid dynamics applied to the case of mixing give accurate results [6]. Few studies have been done on the effect of mixing behavior on reactor performance. Brucato et al. [7] test two advanced modelling approaches using STAR-CD code. A k-ε model was used to analyze turbulence and the SIMPLE (Semi-Implicit Method for Pressure-Linked Equation) iterative algorithm and Guass-Seidel iterative method to solve pressure linked equations and proved that mixing depends on agitation rate and position of impellers. They extended the CFD three dimensional simulations to competitive reactions in a batch process and the results obtained are based on macro mixing assumption and they showed that there was a good agreement between simulation results and experimental values by using k- ε model with CFD flow 3D codes. Forney and Nafia [8] worked on Eddy contact model using CFD to simulate liquid reactions in nearly homogeneous turbulence fluid flow. The results obtained showed that the model for parallel reactions between acid –base – ester in a nearly homogeneous turbulence is as accurate as Monte Carlo/PDF