CPFD Flow Pattern Simulation in Downer Reactors

Authors: Alireza Abbasi ^a,b, Mohammad Ashraful Islam ^a, Paul E. Ege ^b, and Hugo I. de Lasa ^a
a Dept. of Chemical and Biochemical Engineering, The University of Western Ontario, London, ON, Canada
^b Reactech Process Development Inc., Markham, ON, Canada

Source: Abbasi, A.; Islam, M. A.; Ege, P. E.; de Lasa, H. I. CPFD Flow Pattern Simulation in Downer Reactors. AIChE Journal 2013, 59 (5), 1635–1647.

Abstract: This study contributes with a computational fluid dynamic simulation based on the numerical solution of continuity and momentum balance equations in a three‐dimensional (3‐D) framework. The proposed down flow gas–solid suspension model includes a unit configuration and C_D drag coefficients recommended for these units. Computational particle fluid dynamics (CPFD) calculations using suitable boundary conditions and a Barracuda (version: 14.5.2) software allow predicting local solid densification and asymmetric “wavy flows.” In addition, this model forecasts for the conditions of this study higher particle velocity than gas velocity, once the flow reaches 1 m from the gas injector. These findings are accompanied with observations about the intrinsic rotational character of the flow. CPFD numerical 3‐D calculations show that both gas and particle velocities involve the following: (a) an axial velocity component, (b) a radial velocity component (about 5% of axial velocity component), and (c) an angular velocity component. The calculated velocity components and the rotational flow pattern are established for a wide range of solid flux/gas flux ratios. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1635–1647, 2013