Computational Fluid Dynamics Simulation Of Fluidized Bed Polymerization Reactors
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Computational Fluid Dynamics Simulation Of Fluidized Bed Polymerization Reactors
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Author : Rong Fan
language : en
Publisher:
Release Date : 2006
Computational Fluid Dynamics Simulation Of Fluidized Bed Polymerization Reactors written by Rong Fan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.
In this research, a CFD algorithm for simulation of fluidized bed polymerization reactors is described. In order to properly model the evolution of a polydisperse solid phase, population balance equation (PBE) must be solved along with other transport equations. A novel approach - DQMOM is applied to polydisperse fluidized bed to simulate particle aggregation and breakage in the reactors. Two different aggregation and breakage kernels are tested and the performance of the DQMOM approximation with different numbers of nodes are compared. Results show that the approach is very effective in modeling solid segregation and elutriation and in tracking the evolution of the PSD, even though it requires only a small number of scalars. After successfully developed DQMOM-multi-fluid CFD model, the multi-fluid model is validated with available experiments and discrete particle simulation (DPS). The results show good agreements with experiment data for binary system and DPS results, and the simulations can describe segregation and mixing behavior in the fluidized bed. After the model development and validation, 2D and 3D simulations are conducted for a pilot-scale polymerization fluidized bed at operating conditions. Significant differences are observed between 2D and 3D simulations. The results shows that, for an industrial-scale fluidized bed, only 3D simulations are able to match the statics (bed height and pressure drop) and the dynamics (pressure power spectra) properties of the bed. The residence time for a polyethylene pilot reactor is on the order of hours, and the time scale for the fluid dynamics in the bed is on the seconds. It is impossible to run a three-dimensional simulation for hours using current CFD codes. Due to the time scale problem, a chemical reaction engineering model based on the age of particles is combined with multi-fluid model to initialize the fluidized bed to a steady state. Direct quadrature method of moments (DQMOM) is used to simulate the particle size distribution in the bed. The hot spots in the fluidized bed are also investigated using CFD simulations.
Computational Fluid Dynamics Simulation Of Fluidized Bed Polymerization Reactors
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Author :
language : en
Publisher:
Release Date : 2006
Computational Fluid Dynamics Simulation 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 2006 with categories.
Fluidized beds (FB) reactors are widely used in the polymerization industry due to their superior heat- and mass-transfer characteristics. Nevertheless, problems associated with local overheating of polymer particles and excessive agglomeration leading to FB reactors defluidization still persist and limit the range of operating temperatures that can be safely achieved in plant-scale reactors. Many people have been worked on the modeling of FB polymerization reactors, and quite a few models are available in the open literature, such as the well-mixed model developed by McAuley, Talbot, and Harris (1994), the constant bubble size model (Choi and Ray, 1985) and the heterogeneous three phase model (Fernandes and Lona, 2002). Most these research works focus on the kinetic aspects, but from industrial viewpoint, the behavior of FB reactors should be modeled by considering the particle and fluid dynamics in the reactor. Computational fluid dynamics (CFD) is a powerful tool for understanding the effect of fluid dynamics on chemical reactor performance. For single-phase flows, CFD models for turbulent reacting flows are now well understood and routinely applied to investigate complex flows with detailed chemistry. For multiphase flows, the state-of-the-art in CFD models is changing rapidly and it is now possible to predict reasonably well the flow characteristics of gas-solid FB reactors with mono-dispersed, non-cohesive solids. This thesis is organized into seven chapters. In Chapter 2, an overview of fluidized bed polymerization reactors is given, and a simplified two-site kinetic mechanism are discussed. Some basic theories used in our work are given in detail in Chapter 3. First, the governing equations and other constitutive equations for the multi-fluid model are summarized, and the kinetic theory for describing the solid stress tensor is discussed. The detailed derivation of DQMOM for the population balance equation is given as the second section. In this section, monovariate population balance, bivariate population balance, aggregation and breakage equation and DQMOM-Multi-Fluid model are described. In the last section of Chapter 3, numerical methods involved in the multi-fluid model and time-splitting method are presented. Chapter 4 is based on a paper about application of DQMOM to polydisperse gas-solid fluidized beds. Results for a constant aggregation and breakage kernel and a kernel developed from kinetic theory are shown. The effect of the aggregation success factor and the fragment distribution function are investigated. Chapter 5 shows the work on validation of mixing and segregation phenomena in gas-solid fluidized beds with a binary mixture or a continuous size distribution. The simulation results are compared with available experiment data and discrete-particle simulation. Chapter 6 presents the project with Univation Technologies on CFD simulation of a Polyethylene pilot-scale FB reactor, The fluid dynamics, mass/heat transfer and particle size distribution are investigated through CFD simulation and validated with available experimental data. The conclusions of this study and future work are discussed in Chapter 7.
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.
Modeling And Simulation Of Fluidized Bed Reactors For Chemical Looping Combustion
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Author : Ramesh K. Agarwal
language : en
Publisher: Springer
Release Date : 2023-12-17
Modeling And Simulation Of Fluidized Bed Reactors For Chemical Looping Combustion written by Ramesh K. Agarwal and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-12-17 with Technology & Engineering categories.
The book describes the clean coal technology of chemical looping combustion (CLC) for power generation with pure CO2 capture. The focus of the book is on the modeling and simulation of CLC. It includes fundamental concepts behind CLC and considers all categories of fluidized beds and reactors, including a variety of oxygen carriers. The book includes process simulations with Aspen Plus® software using coal, natural gas, and biomass and computational fluid dynamics (CFD) simulations using both the Eulerian and Lagrangian methods. It describes various drag models, turbulence models, and kinetics models required for CFD simulations of CLC and covers single reactor, partial, and full-simulations, single/multi-stage as well as single-particle simulations, and CLC with reverse flow. A large number of examples for both process simulations using Aspen Plus and CFD simulations using a variety of fluidized beds/reactors employing both the two-fluid and Computational Fluid Dynamics / Discrete Element Method (CFD-DEM) model are provided. Modeling and Simulation of Fluidized Bed Reactors for Chemical Looping Combustion will be an invaluable reference for industry practitioners and researchers in academic and industrial R&D currently working on clean energy technologies and power generation with carbon capture.
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.
Computational Fluid Dynamics Modeling And Simulations Of Fluidized Bed Reactors For Chemical Looping Combustion
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Author : Subhodeep Banerjee
language : en
Publisher:
Release Date : 2016
Computational Fluid Dynamics Modeling And Simulations Of Fluidized Bed Reactors For Chemical Looping Combustion written by Subhodeep Banerjee 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.
Chemical looping combustion (CLC) is a next generation combustion technology that shows great promise as a solution for the need of high-efficiency low-cost carbon capture from fossil fueled power plants. To realize this technology on an industrial scale, the development of high-fidelity simulations is a necessary step to develop a thorough understanding of the CLC process. Although there have been a number of experimental studies on CLC in recent years, CFD simulations have been limited in the literature.In this dissertation, reacting flow simulations of a CLC reactor are developed using the Eulerian approach based on a laboratory-scale experiment of a dual fluidized bed CLC system. The salient features of the fluidization behavior in the air reactor and fuel reactor beds representing a riser and a bubbling bed respectively are accurately captured in the simulation. This work is one of the first 3-D simulations of a complete circulating dual fluidized bed system; it highlights the importance of conducting 3-D simulations of CLC systems and the need for more accurate empirical reaction rate data for future CLC simulations.Simulations of the multiphase flow with chemical reactions in a spouted bed fuel reactor for coal-direct CLC are performed based on the Lagrangian particle tracking approach. The Discrete Element Method (DEM) provides the means for tracking the motion of individual metal oxide particles in the CLC system as they react with the fuel and is coupled with CFD for capturing the solid-gas multiphase hydrodynamics. The overall results of the coupled CFD-DEM simulations using Fe-based oxygen carriers reacting with gaseous CH4 demonstrate that chemical reactions have been successfully incorporated into the CFD-DEM approach. The simulations show a strong dependence of the fluidization performance of the fuel reactor on the density of bed material and provide important insight into selecting the right oxygen carrier for the enhanced performance.Given the high computing cost of CFD-DEM, it is necessary to develop a scaling methodology based on the principles of dynamic similarity that can be applied to expand the scope of this approach to larger CLC systems up to the industrial scale. A new scaling methodology based on the terminal velocity is proposed for spouted fluidized beds. Simulations of a laboratory-scale spouted fluidized bed are used to characterize the performance of the new scaling law in comparison with existing scaling laws in the literature. It is shown that the new model improves the accuracy of the simulation results compared to the other scaling methodologies while also providing the largest reduction in the number of particles and in turn in the computing cost.CFD-DEM simulations are conducted of the binary particle bed associated with a coal-direct CLC system consisting of coal (represented by plastic beads) and oxygen carrier particles and validated against an experimental riser-based carbon stripper. The simulation results of the particle behavior and the separation ratio of the particles are in excellent agreement with the experiment. A credible simulation of a binary particle bed is of particular importance for understanding the details of the fluidization behavior; the baseline simulation established in this work can be used as a tool for designing and optimizing the performance of such systems.The simulations conducted in this dissertation provide a strong foundation for future simulations of CD-CLC systems using solid coal as fuel, considering the additional complexities associated with the changing density and diameter of the coal particles as devolatilization and gasification process occur. A complete reacting flow simulation in the CFD-DEM framework will be crucial for the successful deployment of CD-CLC technology from the laboratory scale to pilot and industrial scale projects.
Design And Modeling Of A Fluidized Bed Reactor Using Computational Fluid Dynamics
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Author : Mark More
language : en
Publisher:
Release Date : 2010
Design And Modeling Of A Fluidized Bed Reactor Using Computational Fluid Dynamics written by Mark More and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Fluid dynamics categories.
Fluidized Bed Reactors Processes And Operating Conditions
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Author : John G. Yates
language : en
Publisher: Springer
Release Date : 2016-09-27
Fluidized Bed Reactors Processes And Operating Conditions written by John G. Yates and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-09-27 with Science categories.
The fluidized-bed reactor is the centerpiece of industrial fluidization processes. This book focuses on the design and operation of fluidized beds in many different industrial processes, emphasizing the rationale for choosing fluidized beds for each particular process. The book starts with a brief history of fluidization from its inception in the 1940’s. The authors present both the fluid dynamics of gas-solid fluidized beds and the extensive experimental studies of operating systems and they set them in the context of operating processes that use fluid-bed reactors. Chemical engineering students and postdocs as well as practicing engineers will find great interest in this book.
Computational Particle Fluid Dynamics Simulations Of A Commercial Scale Turbulent Fluidized Bed Reactor
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Author : Paul Zhao
language : en
Publisher:
Release Date : 2006
Computational Particle Fluid Dynamics Simulations Of A Commercial Scale Turbulent Fluidized Bed Reactor written by Paul Zhao and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Chemical engineering categories.
Computational Modeling Of Circulating Fluidized Bed Reactors
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Author :
language : en
Publisher:
Release Date : 2013
Computational Modeling Of Circulating Fluidized Bed 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 2013 with categories.
Details of numerical simulations of two-phase gas-solid turbulent flow in the riser section of Circulating Fluidized Bed Reactor (CFBR) using Computational Fluid Dynamics (CFD) technique are reported. Two CFBR riser configurations are considered and modeled. Each of these two riser models consist of inlet, exit, connecting elbows and a main pipe. Both riser configurations are cylindrical and have the same diameter but differ in their inlet lengths and main pipe height to enable investigation of riser geometrical scaling effects. In addition, two types of solid particles are exploited in the solid phase of the two-phase gas-solid riser flow simulations to study the influence of solid loading ratio on flow patterns. The gaseous phase in the two-phase flow is represented by standard atmospheric air. The CFD-based FLUENT software is employed to obtain steady state and transient solutions for flow modulations in the riser. The physical dimensions, types and numbers of computation meshes, and solution methodology utilized in the present work are stated. Flow parameters, such as static and dynamic pressure, species velocity, and volume fractions are monitored and analyzed. The differences in the computational results between the two models, under steady and transient conditions, are compared, contrasted, and discussed.