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Abbasi A.,University of Western Ontario | Abbasi A.,Reactech Process Development Inc. | Ege P.E.,Reactech Process Development Inc. | de Lasa H.I.,University of Western Ontario
Chemical Engineering Journal | Year: 2011

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 PFR. 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 2D CPFD model is particularly useful for describing fast fluidized beds operation involving significant amounts of rich ash recycled feeds. © 2011.


Abbasi A.,University of Western Ontario | Abbasi A.,Reactech Process Development Inc. | Islam M.A.,University of Western Ontario | Ege P.E.,Reactech Process Development Inc. | De Lasa H.I.,University of Western Ontario
11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings | Year: 2011

A downer reactor is suitable for the enhancement of a diversity of chemical processes, e.g., FCC process, residual oil cracking, and biomass and coal pyrolysis. It is essential to understand the macro as well as the micro-structural behavior of gas-solid flow in a downer reactor for reactor scale-up. A fluid dynamic simulation based on the numerical solution of continuity and momentum balance equations in a three-dimensional framework using Barracuda's software is carried out. The proposed model includes a reactor configuration and specific CD drag coefficients recommended for downflow reactors. The Computational Particle Fluid Dynamics (CPFD) simulation conditions represent actual flow conditions likely to be used in a gas-solid downflow reactor unit with FCC particles. Model results are established in the context of stabilized solid and fluid flow patterns. The CPFD model predicts local densification of solids and asymmetric wavy flows. The model also forecasts higher particle velocity than gas velocity, once the flow reaches an axial position > 1 m from the gas injector. This is an abstract of a paper presented at the 2011 AIChE Annual Meeting (Minneapolis, MN 10/16-21/2011).


Abbasi A.,University of Western Ontario | Abbasi A.,Reactech Process Development Inc. | Islam M.A.,University of Western Ontario | Ege P.E.,Reactech Process Development Inc. | De Lasa H.I.,University of Western Ontario
Powder Technology | Year: 2012

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. © 2012 Elsevier B.V.

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