Kinetic Theory Of Granular Flows And Multi Scale Cfd Modeling For Fluidized Beds
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Kinetic Theory Of Granular Flows And Multi Scale Cfd Modeling For Fluidized Beds
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Author : Yujian Sun
language : en
Publisher:
Release Date : 2016
Kinetic Theory Of Granular Flows And Multi Scale Cfd Modeling For Fluidized Beds written by Yujian Sun and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with Electronic dissertations categories.
Fluidized beds are widely used in chemical industry for carrying out gas-solids reactions. Their advantages include superior heat transfer, low pressure drop compared to fixed beds, high throughput, and the ability to regenerate or reprocess the spent particles in a separate unit from the main reactor, when operated in a circulating fluidized bed mode. In spite of these desirable features, this type of gas-solids contactors also present challenges in understanding the detailed hydrodynamics, mixing and contacting pattern, as well as their effects on reactions. Design of commercial fluidized beds often requires scale-up from a smaller lab or pilot plant, but the behavior of the different scales must be linked by proper reactor models that take into account the possible changes in hydrodynamics and contacting patterns between the scales. This can be challenging because the prediction and extension of key parameters used in a model, such as axial dispersion number is usually not available, and phenomenological models for these parameters based on science are often missing. To meet these challenges, computational fluid dynamics, or CFD, can be utilized as a tool to extract the needed information by coarse-graining from the detailed hydrodynamics of the multiphase system, thus aiding in more rational design and scale-up of fluidized bed reactors. The CFD models in turn have their own parameters that need phenomenological models, which xii are easier to construct from fundamentals. Two types of simulation methods, i.e. Eulerian-Eulerian and Eulerian-Lagrangian, are investigated in this study. For the Eulerian method (also called two-fluid model, or TFM), in which the discrete solid particles are assumed as a continuous granular phase interpenetrated with the gas, the constitutive models for solids phase stress are needed. In this work, a new set of such models is developed from kinetic theory of granular flows with a new collision model. In this model, both the normal and tangential part of relative velocity between two colliding particles is damped due to inelastic collision, while the traditional model only takes into account the normal part. With this modification, the previously under-estimated dissipation rate of fluctuation energy is increased as expected. The models are implemented in OpenFOAM, an open-source CFD platform, to simulate a fluidized bed. The model improves the prediction of solids volume fraction without extra computational cost. In the Lagrangian or DEM (discrete element method) approach, the effort is motivated by Bhusarapus (2005) pioneering finding using CARPT (computer-aided radioactive particle tracking) that the traditional tracer method for measuring solids residence time distribution (RTD) cannot capture the actual residence time due to inability to distinguish the time that a particle temporarily spends out of the riser after first entry to or before last exit from the riser. By implementing the algorithm developed in this work to record separately the time that each particle actually spends in the riser, Lagrangian simulation is performed for a small circulating fluidized bed in OpenFOAM. The results clearly demonstrate the difference between RTD obtained from simulated traditional tracer method and that from the Lagrangian approach. Other information can be extracted as well such as the first passage time distribution, macromixing index, and interchange coefficient between a core region and an annular region, if using a core-annulus model. The potential capability of this CFD approach is boundless.
Computational Fluid Dynamic Modeling Of Fluidized Bed Polymerization Reactors
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Author :
language : en
Publisher:
Release Date : 2012
Computational Fluid Dynamic Modeling Of Fluidized Bed Polymerization Reactors written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Polyethylene is one of the most widely used plastics, and over 60 million tons are produced worldwide every year. Polyethylene is obtained by the catalytic polymerization of ethylene in gas and liquid phase reactors. The gas phase processes are more advantageous, and use fluidized-bed reactors for production of polyethylene. Since they operate so close to the melting point of the polymer, agglomeration is an operational concern in all slurry and gas polymerization processes. Electrostatics and hot spot formation are the main factors that contribute to agglomeration in gas-phase processes. Electrostatic charges in gas phase polymerization fluidized bed reactors are known to influence the bed hydrodynamics, particle elutriation, bubble size, bubble shape etc. Accumulation of electrostatic charges in the fluidized-bed can lead to operational issues. In this work a first-principles electrostatic model is developed and coupled with a multi-fluid computational fluid dynamic (CFD) model to understand the effect of electrostatics on the dynamics of a fluidized-bed. The multi-fluid CFD model for gas-particle flow is based on the kinetic theory of granular flows closures. The electrostatic model is developed based on a fixed, size-dependent charge for each type of particle (catalyst, polymer, polymer fines) phase. The combined CFD model is first verified using simple test cases, validated with experiments and applied to a pilot-scale polymerization fluidized-bed reactor. The CFD model reproduced qualitative trends in particle segregation and entrainment due to electrostatic charges observed in experiments. For the scale up of fluidized bed reactor, filtered models are developed and implemented on pilot scale reactor.
Dynamically Structured Flow In Pulsed Fluidised Beds
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Author : Kaiqiao Wu
language : en
Publisher: Springer Nature
Release Date : 2021-03-27
Dynamically Structured Flow In Pulsed Fluidised Beds written by Kaiqiao Wu and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-03-27 with Science categories.
This book analyses the use of a pulsed gas flow to structure bubbling gas-solid fluidised beds and to induce a special fluidisation state, called "dynamically structured flow", as a promising approach to process intensification. It explores the properties of bubbles rising in staggered periodic arrays without direct interaction, assessing their size, separation, and velocity, and explains how a highly uniform, scalable flow offers tight control over the system hydrodynamics. These features are desirable, as they not only bypass engineering challenges occurring in traditional operations, such as maldistribution and non-uniform contact, but also allow to decouple conflicting design objectives, such as mixing and gas-solid contact. The thesis also presents computational simulations which reveal the periodic transitions of the particulate phase between fluid-like and solid-like behaviour. This book will be of interest to researchers, engineers, and graduate students alike, particularly those working in industrial drying, combustion, and chemical production.
Use Of Cfd For The Extrapolation Of Attrition And Hydrodynamic Phenomena In Circulating Fluidized Beds
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Author : Benjamin Amblard
language : en
Publisher:
Release Date : 2020
Use Of Cfd For The Extrapolation Of Attrition And Hydrodynamic Phenomena In Circulating Fluidized Beds written by Benjamin Amblard and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
Extrapolation from lab to industrial scale is challenging when dealing with Circulating Fluidized Bed (CFB) processes and technologies. Extrapolation relates in a first step, to the understanding of physical phenomena at accessible scales through dedicated experiments. In a second step, modeling is often used to transpose observation from lab scale to an industrial perspective. In my Ph.D. project, we present how Computational Fluid Dynamic (CFD) tools can be used for both steps with first the characterization of local phenomena at lab scale and second for the scale extrapolation of hydrodynamic phenomena. Concerning the first topic, it is essential in the early stage of the process development, to quantify attrition phenomena expected at industrial scale when selecting the solid particles to be used. We faced this situation during the development of the Chemical Looping Combustion (CLC) process with the choice of the oxygen carrier particles. We then proposed a new procedure using a jet cup apparatus to compare the mechanical resistance to attrition of particles used in the CLC process with particles used in the Fluid Catalytic Cracking (FCC) process. The latter is then used as a reference since attrition data are available both at lab and industrial scales for FCC catalyst. We used CFD tools for the understanding of local physical phenomena to then orientate the experimental strategy to compare the mechanical resistance to attrition of the different powders of interest (equilibrium FCC catalyst and fresh and equilibrium oxygen carriers). The results obtained showed that the fresh and equilibrium oxygen carriers performed respectively better and worse than the reference FCC catalyst. This experimental procedure can therefore be used in the future to evaluate the mechanical resistance of other oxygen carriers. The main perspective is then to correlate lab scale experimentation with the main sources of attrition in CFBs for finally implementing a population balance modeling to assess attrition at industrial scale.Concerning the second topic on hydrodynamic phenomena extrapolation, we propose a simulation strategy in order to assess the CFD models extrapolation capability and their potential limits in term of fluidization regimes representativeness. For this purpose, different experimental set ups were used with a 20 cm and 90 cm turbulent fluidized beds and a 30 cm riser to characterize transport regime conditions. In the three experiments, FCC catalysts with similar physical properties were used. Local and global experimental flow characterizations were acquired to then evaluate the predictions of two CFD approaches: the Multiphase Particle In Cell (MP-PIC) approach with the software Barracuda VR® and the Euler/Euler with the Kinetic Theory of Granular Flows using openFOAM. In the first step, we developed dedicated drag laws to get satisfactory hydrodynamic predictions of the 20 cm fluidized bed hydrodynamic. In the next step, the CFD model parameters developed were applied for the 90 cm fluidized bed simulation. This step was crucial since it was a differentiator between both approaches with the parameters developed for Barracuda VR® failing to predict the bed hydrodynamic while the parameters developed for openFOAM gave satisfying results. These results justify the evaluation of CFD models at different scales and also show that CFD can be used for extrapolation. In the last step, the openFOAM modeling parameters developed were applied for the simulation of the riser transport regime. The simulation failed capturing the riser hydrodynamic and a dedicated drag law was then developed to capture reasonably well these riser experimental data. These results show the importance of investigating the limits of the models developed. For the perspectives, the same strategy could be applied for the predictions of pressure and temperature effects with the final objective being to simulate an industrial fluidized bed.
Computational Flow Modeling For Chemical Reactor Engineering
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Author : Vivek V. Ranade
language : en
Publisher: Academic Press
Release Date : 2002
Computational Flow Modeling For Chemical Reactor Engineering written by Vivek V. Ranade and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with Science categories.
The book relates the individual aspects of chemical reactor engineering and computational flow modeling in a coherent way to explain the potential of computational flow modeling for reactor engineering research and practice.
Modeling Approaches And Computational Methods For Particle Laden Turbulent Flows
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Author : Shankar Subramaniam
language : en
Publisher: Academic Press
Release Date : 2022-10-20
Modeling Approaches And Computational Methods For Particle Laden Turbulent Flows written by Shankar Subramaniam and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-10-20 with Science categories.
Modelling Approaches and Computational Methods for Particle-laden Turbulent Flows introduces the principal phenomena observed in applications where turbulence in particle-laden flow is encountered while also analyzing the main methods for analyzing numerically. The book takes a practical approach, providing advice on how to select and apply the correct model or tool by drawing on the latest research. Sections provide scales of particle-laden turbulence and the principal analytical frameworks and computational approaches used to simulate particles in turbulent flow. Each chapter opens with a section on fundamental concepts and theory before describing the applications of the modelling approach or numerical method. Featuring explanations of key concepts, definitions, and fundamental physics and equations, as well as recent research advances and detailed simulation methods, this book is the ideal starting point for students new to this subject, as well as an essential reference for experienced researchers. Provides a comprehensive introduction to the phenomena of particle laden turbulent flow Explains a wide range of numerical methods, including Eulerian-Eulerian, Eulerian-Lagrange, and volume-filtered computation Describes a wide range of innovative applications of these models
Computational Fluid Dynamics Cfd Of Chemical Processes
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Author : Young-Il Lim
language : en
Publisher: MDPI
Release Date : 2021-02-22
Computational Fluid Dynamics Cfd Of Chemical Processes written by Young-Il Lim and has been published by MDPI this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-02-22 with Technology & Engineering categories.
In this Special Issue, one review paper highlights the necessity of multiscale CFD, coupling micro- and macro-scales, for exchanging information at the interface of the two scales. Four research papers investigate the hydrodynamics, heat transfer, and chemical reactions of various processes using Eulerian CFD modeling. CFD models are attractive for industrial applications. However, substantial efforts in physical modeling and numerical implementation are still required before their widespread implementation.
Multiphase Flow And Fluidization
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Author : Dimitri Gidaspow
language : en
Publisher: Elsevier
Release Date : 2012-12-02
Multiphase Flow And Fluidization written by Dimitri Gidaspow and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-02 with Science categories.
Useful as a reference for engineers in industry and as an advanced level text for graduate engineering students, Multiphase Flow and Fluidization takes the reader beyond the theoretical to demonstrate how multiphase flow equations can be used to provide applied, practical, predictive solutions to industrial fluidization problems. Written to help advance progress in the emerging science of multiphase flow, this book begins with the development of the conservation laws and moves on through kinetic theory, clarifying many physical concepts (such as particulate viscosity and solids pressure) and introducing the new dependent variable--the volume fraction of the dispersed phase. Exercises at the end of each chapterare provided for further study and lead into applications not covered in the text itself. Treats fluidization as a branch of transport phenomena Demonstrates how to do transient, multidimensional simulation of multiphase processes The first book to apply kinetic theory to flow of particulates Is the only book to discuss numerical stability of multiphase equations and whether or not such equations are well-posed Explains the origin of bubbles and the concept of critical granular flow Presents clearly written exercises at the end of each chapter to facilitate understanding and further study
Granularity In Materials Science
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Author : George Kyzas
language : en
Publisher: BoD – Books on Demand
Release Date : 2018-10-24
Granularity In Materials Science written by George Kyzas and has been published by BoD – Books on Demand this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-10-24 with Science categories.
Granular materials are a special topic of recent research and are a milestone of science and technology. These materials are very simple: they are large conglomerations of discrete macroscopic particles. Granular materials have a broad area of development, which is growing rapidly day by day. Their impact on commercial applications and academia and education is huge. The basic points of this book are the important applications and properties of granular materials. For example, special mention is made of rheological points, shapes, and civil engineering aspects.
Process Systems Engineering For Pharmaceutical Manufacturing
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Author : Ravendra Singh
language : en
Publisher: Elsevier
Release Date : 2018-03-16
Process Systems Engineering For Pharmaceutical Manufacturing written by Ravendra Singh and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-03-16 with Technology & Engineering categories.
Process Systems Engineering for Pharmaceutical Manufacturing: From Product Design to Enterprise-Wide Decisions, Volume 41, covers the following process systems engineering methods and tools for the modernization of the pharmaceutical industry: computer-aided pharmaceutical product design and pharmaceutical production processes design/synthesis; modeling and simulation of the pharmaceutical processing unit operation, integrated flowsheets and applications for design, analysis, risk assessment, sensitivity analysis, optimization, design space identification and control system design; optimal operation, control and monitoring of pharmaceutical production processes; enterprise-wide optimization and supply chain management for pharmaceutical manufacturing processes. Currently, pharmaceutical companies are going through a paradigm shift, from traditional manufacturing mode to modernized mode, built on cutting edge technology and computer-aided methods and tools. Such shifts can benefit tremendously from the application of methods and tools of process systems engineering. Introduces Process System Engineering (PSE) methods and tools for discovering, developing and deploying greener, safer, cost-effective and efficient pharmaceutical production processes Includes a wide spectrum of case studies where different PSE tools and methods are used to improve various pharmaceutical production processes with distinct final products Examines the future benefits and challenges for applying PSE methods and tools to pharmaceutical manufacturing