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Parker J.M.,Cpfd Software, Llc
International Journal of Chemical Reactor Engineering

In this work, a CFD model for simulating industrial scale particle-fluid systems is used to model a fluidized bed reactor for the deposition of high-purity silicon from silane gas. The performance of these reactors is directly dependent on a large number of factors and parameters which make the design and optimization of the deposition reactors an engineering challenge. Using the reactor design and experimental data from work performed at the Jet Propulsion Laboratory as a basis for validation, the CFD model was found to accurately model the deposition rate, silicon fines production, and temperature distribution within a silane deposition reactor. Additionally, the CFD model is demonstrated to be an effective tool for comparing different reactor designs on the basis of fluidization mode, reaction conversion, heat transfer, and particle mixing. Copyright ©2011 The Berkeley Electronic Press. All rights reserved. Source

O'Rourke P.J.,CFD dOR Software and Consulting LLC | Snider D.M.,Cpfd Software, Llc
Chemical Engineering Science

This paper describes several improvements to a numerical model introduced by O'Rourke et al. (2009) for collisional exchange and damping in dense particle flows. O'Rourke et al. (2009) use a Bhatnagar, Gross, and Krook (BGK) approximation to the collision terms in a particle distribution function transport equation to model the effects of particle collisions on damping fluctuating particle velocities and, in gas/liquid/solid beds, fluctuating temperatures and compositions of liquid films on particle surfaces. In this paper we focus on particle flows in which the particles have no liquid films and report on an improved expression we have developed for the collision damping time of particle velocity fluctuations used in the BGK approximation. The improved expression includes the effects on the collision damping time of the particle material coefficient of restitution and of non-equilibrium particle velocity distributions. The collision model improvements are incorporated into the general-purpose computational-particle fluid dynamics (CPFD) numerical methodology for dense particle flows. Three computational examples show the benefits of using the new collision time in calculations of particle separation in polydisperse dense particle flows and calculations of colliding particle jets. © 2010 Elsevier Ltd. Source

Parker J.M.,Cpfd Software, Llc
Powder Technology

A chemical looping combustion (CLC) system uses a metal oxide solid carrier to combust a source of fuel in isolation from the source of oxygen which produces an exhaust gas of primarily carbon dioxide and water. In this work, a full three-dimensional model of a chemical looping combustion system was developed to simulate the particle-fluid hydrodynamics, thermal characteristics, and reaction efficiency of the CLC system using coal particles as a fuel source. Multiple heterogeneous and homogenous reactions are considered in the CLC model including the oxidation and reduction reactions of the metal oxide carrier and gasification reactions. Within each coal particle, the temperature-dependent devolatilization, moisture release, and particle swelling effects are included. Modeling results showing fluidization regimes, circulation rate, reactor efficiencies, and temperature profiles are presented to demonstrate the utility of the model. © 2014 Elsevier B.V. Source

Blaser P.J.,Cpfd Software, Llc
International Journal of Chemical Reactor Engineering

The 40 MW Strongoli power plant, located in the Calabria region of Italy, produces power from 100% biomass sources. The combustion of wood biomass, exhausted olive residues and palm kernel shells, occurs in a sand-filled, Circulating Fluidized Bed (CFB) combustor. Operational experience with the unit dates back to 2003. This paper describes the optimization of the boiler in order to minimize erosion on internal surfaces and structures. Detailed three-dimensional, transient, multiphase gas-solid flow fields were computed and are presented. Details of the complex geometry include the combustion chamber, cyclone, cyclone dipleg, seal pot, fluidized bed heat exchanger and cyclone outlet structures including suspension tubes. The gas-solid flow was computed using the commercially-available software package Barracuda, a CFD software based on a unique Eulerian-Lagrangian formulation that was essential to the success of the subject work. Both instantaneous and time-averaged results were obtained. Results were validated against operational erosion experience. The validated model, in turn, was utilized to redesign various components of the boiler, optimizing both erosion characteristics and performance behaviour of the system. The redesigned unit was commissioned in early 2012. Copyright © 2012 De Gruyter. All rights reserved. Source

Snider D.,Cpfd Software, Llc | Banerjee S.,Cristal Global
Powder Technology

Heterogeneous catalytic chemistry is used throughout the chemical and petro-chemical industry. In predicting the performance of a reactor, knowing the gases and solids flow dynamics is as important as having good chemical rate expressions. This paper gives the solution of ozone decomposition in a bubbling bed using the CPFD numerical scheme which is a Eulerian-Lagrangian solution method for fluid-solid flows. The ozone decomposition can be described by a single stoichiometric equation and has a first order reaction rate. The ozone decomposition is a standard problem for chemical analysis and has been used to characterize gas-solid contacts in fluidized beds. The accuracy of predicting the ozone decomposition comes from correctly predicting the bed dynamics. The solution in this study is three-dimensional and predicts the coupled motion of both solids and gas. The chemical rate equation uses solids volume fraction, but the numerical method could calculate chemistry on the discrete catalyst, including a variation in size (surface area) if such a rate equation was available. The numerical results compare well with an analytic solution of the decomposition rate, and calculated results compare well with the experiment by Fryer and Potter [Fryer, C. and Potter, O.E, (1976), "Experimental investigation of models for fluidized bed catalytic reactors," AIChE J., 22.]. © 2009 Elsevier B.V. All rights reserved. Source

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