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CPFD Flow Pattern Simulation in Downer Reactors

AICHE JOURNAL 2013年第5期59卷 1635-1647页

作者： Abbasi, Alireza Islam, Mohammad Ashraful Ege, Paul E. de lasa, Hugo I. Univ Western Ontario Dept Chem & Biochem Engn London ON N6A 5B9 Canada Reactech Proc Dev Inc Markham ON Canada

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 CD 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. (C) 2012 American Institute of Chemical Engineers AIChE J, 59: 1635-1647, 2013

关键词： fluidization down flow reactors computational fluid dynamics particulate systems CREC-GS Optiprobes

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Downer reactor flow measurements using CREC-GS-Optiprobes

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POWDER TECHNOLOGY 2012年 224卷 1-11页

作者： Abbasi, Alireza Islam, Mohammad Ashraful Ege, Paul E. de Lasa, Hugo I. Univ Western Ontario Dept Chem & Biochem Engn London ON N6A 5B9 Canada Reactech Proc Dev Inc Markham ON Canada

The present study describes the potential intrusive effects of CREC-GS-Optiprobes on the flow pattern in gas-solid downflow units. Granular flows and their interactions with the CREC-GS-Optiprobes are calculated using a CPFD (Computational Particle Fluid Dynamic) numerical scheme in three dimensions, using particle clusters. Once particles dispersed in the column, the numerical simulations revealed that these particles formed a relatively homogeneous suspension with cluster formation and solids accelerating until reaching a fully-developed regime. CPFD simulations showed that two axially aligned CREC-GS-Optiprobes, when placed in the fully developed flow regime, introduce minimum perturbations in the gas-solid suspension. Therefore this CREC-GS-Optiprobe creates a highly illuminated focal region where hydrodynamic parameters can be measured without significant flow disturbance. Thus, this study supports the application of fiber optic probes;such as in the case of the CREC-GS-Optiprobes, which can provide undisturbed axial particle cluster velocity, axial cluster slip velocities, cluster size and solid fraction measurements at strategically selected locations in the gas-solid downer unit. (C) 2012 Elsevier B.V. All rights reserved.

关键词： Optical sensors Downer units CPFD simulation Cluster particle velocity

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CPFD simulation of a fast fluidized bed steam coal gasifier feeding section

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CHEMICAL ENGINEERING JOURNAL 2011年第1期174卷 341-350页

作者： Abbasi, Alireza Ege, Paul E. de lasa, Hugo I. Univ Western Ontario Dept Chem & Biochem Engn London ON N6A 5B9 Canada Reactech Proc Dev Inc Markham ON Canada

Coal gasification in fluidized beds is a process that can be strongly influenced by gas-solid suspension flow patterns. Fast fluidized beds can be designed to maximize coal gasification yields providing an optimum syngas composition with minimum operational upsets. In order to accomplish this, a comprehensive model for steam coal gasification is valuable. With this end, a 2D CPFD (computational particle fluid dynamics) dynamic model is considered in the present study. The proposed model uses a Lagrangian-Eulerian approach and describes the flow patterns in the gasifier feeding section, as well as the local particle velocities, particle solid fractions and gas composition. As a reference and for comparison, an ideal PFR (plug flow reactor) model is also considered. It is found that compositions from the 2D CPFD model provide close gas compositions with respect to the PER. It is observed that the 2D CPFD model is valuable for predicting particle flows in the feeding near region keeping it unaffected by fast fluidized bed upsets such as suspension chocking. It is also found that the 20 CPFD model is particularly useful for describing fast fluidized beds operation involving significant amounts of rich ash recycled feeds. (C) 2011 Published by Elsevier B.V.

关键词： Coal gasification Fluidized beds Computational particle fluid dynamics Suspension chocking

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