Particle Resolved Simulations Of Particle Flow Interactions In Fluidized Beds To Optimize Design And Operation Of Domestic Wastewater Treatment Systems
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Particle Resolved Simulations Of Particle Flow Interactions In Fluidized Beds To Optimize Design And Operation Of Domestic Wastewater Treatment Systems
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Author : Yinuo Yao
language : en
Publisher:
Release Date : 2021
Particle Resolved Simulations Of Particle Flow Interactions In Fluidized Beds To Optimize Design And Operation Of Domestic Wastewater Treatment Systems written by Yinuo Yao and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
Recently, the Staged Anaerobic Fluidized-bed Membrane Bioreactor (SAF-MBR), which consists of an anaerobic fluidized-bed reactor (AFBR) and a particle-sparged membrane bioreactor (P-MBR), has been developed to reduce the energy intensity of domestic wastewater treatment by using anaerobic microorganisms that convert organics into methane in the absence of aeration. While this has the potential to transform domestic wastewater treatment into an energy positive process, the moving particles in the SAF-MBR induce hydrodynamic processes related to flow-particle and particle-particle interactions that are poorly understood. With a better understanding of hydrodynamics, better design and operational practices can be developed. In this dissertation, a collocated particle resolved simulation (PRS) using the immersed boundary method (IBM) is developed to accurately quantify the fluid-particle and particle-particle interactions in a fluidized-bed reactor. This dissertation first investigates the effect of particle Reynolds number which is essentially a nondimensional flow rate that controls the bed expansion. Results imply the existence of an intermediate particle Reynolds number regime at which the combined effect of flow and collisions is optimal and both mixing in the AFBR and membrane scouring in the P-MBR are expected to be maximized. While the Reynolds number is a critical parameter, the design of fluidized beds depends critically on the Archimedes number that combines the effect of particle and fluid properties. Simulation results reveal that particles with Archimedes number greater than roughly 1000 should be used to avoid flow short-circuiting due to clusters in the AFBR and reduced membrane scouring due to ineffective collisions in the P-MBR. In industrial applications, fluidized beds typically contain particles of different sizes that tend to segregate into layers in which the particle size increases moving upward. Our simulations reveal that segregated layers behave identically as they would in their corresponding monodispersed fluidized bed layers. However, the transition region between the two segregated layers cannot be described as a simple superposition of the two segregated layers.
Quantification Of Numerical And Modeling Errors In Simulation Of Fluid Flow Through A Fixed Particle Bed
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Author : Annette Volk
language : en
Publisher:
Release Date : 2015
Quantification Of Numerical And Modeling Errors In Simulation Of Fluid Flow Through A Fixed Particle Bed written by Annette Volk and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
Detailed description of flow through stationary particle beds is crucial for the design and implementation of municipal water filtration, material extraction systems for nuclear waste and industrial water purification systems. Knowledge of fluid-particle interactions and fluid flow properties through the bed is essential to design, but difficult to determine from experimental investigations. Combined granular-fluid simulation methods such as coupled Computational Fluid Dynamics and Discrete Element Method (CFD-DEM) have been used to bridge this gap in fundamental knowledge. Able to capture details of the small-scale and large-scale interactions that are difficult to study in physical beds, simulation findings have added great understanding to this field. Unfortunately, the reported results are occasionally flawed by a lack of understanding, specifically regarding the magnitude of numerical and modeling errors. Uniform reporting of error, investigations of simulation trend, and proof of mesh-independence have not been performed for granular-fluid simulations. A standard method of open-source granular-fluid flow simulation known as CFDEM is applied to the simulation of flow through a fixed bed. The Ergun equation is a validated empirical expression used to predict the drag force in fixed bed flow and this prediction is compared directly to simulation results. A grid-refinement procedure, standard for publication of CFD simulation results, is applied to the CFD-DEM simulations. The solution trend over the refinement range is investigated using the frequency of convergence, convergence types, and the proposed `offset' method; a comparison of the expected numerical error and actual extrapolated solution error. An optimal grid size resulting in the least amount of error is investigated by solution trend, drag profile comparison, and the grid-refinement study results. Error is seen to increase in the simulations at both large cell sizes and as the cell size approaches one particle diameter. A new grid-refinement study application that does not require analytical solution data is shown to be a good predictor of relative error in the grid solutions. Three drag correlations are applied to model fluid flow through a fixed bed. The Gidaspow drag correlation is an exact representation of the Ergun equation, and shows high accuracy. The Di Felice correlations is a continuous-function representation of expected drag force. The Koch-Hill correlation was developed from LB simulations for fluidization conditions, and is chosen as an example of a poor correlation choice. The grid-refinement study results are able to distinguish the poor performance of the Koch-Hill correlation from the highly accurate Gidaspow and Di-Felice correlations. The standard grid-refinement study is shown to be applicable to granular-fluid flows, and to produce results that are useful for common modeling choices. Relatively low convergence frequency of the grid-refinement studies is expected to hinder future application by requiring additional grid solutions. This procedure is recommended for all granular-flow simulations since it provides useful information which can prevent common modeling errors that have hampered fluidization research.
Development And Experimental Validation Of A Discrete Particle Simulation For Fluidized Beds With External And Inter Particle Forces
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Author : Brian Patrick Reed
language : en
Publisher:
Release Date : 2006
Development And Experimental Validation Of A Discrete Particle Simulation For Fluidized Beds With External And Inter Particle Forces written by Brian Patrick Reed and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Fluidization categories.
Traditional modeling of fluidized bed operations has focused on the development of models and correlations for specific systems or narrow areas of application. With recent advances in computing power, new methods of modeling fluidization are possible. One such approach is the Computational Fluid Dynamic Discrete Particle Method (CFD-DPM), which treats the fluid as a continuum and the particles as discrete Newtonian entities. The promise of the CFD-DPM approach lies in its ability to incorporate particle interactions in a way that previous models could not. One area of fluidization that has not been actively modeled is the inclusion of non-traditional forces in the fluidization operation. As an example, the use of external magnetic fields in fluidization has provided some interesting applications including; fluidized beds capable of operation in micro-gravity, manipulation of bed structure, and stabilizing bubbling fluidized beds. The ability to model external forces and particle interactions would increase our understanding of these phenomena and potentially lead to new applications for fluidization. A Computational Fluid Dynamic Discrete Particle Method code, named Particle-X, is developed from first principles. The development includes the consideration of external fields and forces, as well as inter-particle forces. The code is validated against experimental data collected from a variety of fluidized bed operations. Particle-X can be used as a tool for the scientific investigation of fluidization under conditions that cannot be accurately reproduced in a laboratory environment; specifically the development of various fluidization operations for use in micro-gravity is considered.
Particle Flow Within The Pulsed Liquid Solid Fluidized Bed
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Author : Katrin Kelm
language : en
Publisher:
Release Date : 2022
Particle Flow Within The Pulsed Liquid Solid Fluidized Bed written by Katrin Kelm and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with categories.
Spouted And Spout Fluid Beds
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Author : Norman Epstein
language : en
Publisher: Cambridge University Press
Release Date : 2010-12-23
Spouted And Spout Fluid Beds written by Norman Epstein and has been published by Cambridge University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010-12-23 with Technology & Engineering categories.
Since the pioneering text by Mathur and Epstein over 35 years ago, much of the work on this subject has been extended or superseded, producing an enormous body of scattered literature. This edited volume unifies the subject, pulling material together and underpinning it with fundamental theory to produce the only complete, up-to-date reference on all major areas of spouted bed research and practice. With contributions from internationally renowned research groups, this book guides the reader through new developments, insights and models. The hydrodynamic and reactor models of spouted and spout-fluid beds are examined, as well as such topics as particle segregation, heat and mass transfer, mixing and scale-up. Later chapters focus on drying, particle-coating and energy-related applications based on spouted and spout-fluid beds. This is a valuable resource for chemical and mechanical engineers in research and industry.
Particle Fluidization In Upward And Inverse Liquid Solid Circulating Fluidized Bed
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Author : Long Sang
language : en
Publisher:
Release Date : 2013
Particle Fluidization In Upward And Inverse Liquid Solid Circulating Fluidized Bed written by Long Sang 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.
The fluidization of particles in upwards and inverse Liquid-Solid Circulating Fluidized Bed is carried out to investigate the hydrodynamic characteristics when using?heavy? and?light? particles, whose densities are higher and lower than that of the surrounding liquid respectively. Generally, the solids are fluidized upwards in the former case, whereas, the downwards fluidization is preferred in the latter scenario. In the Liquid-Solid Circulating Fluidized Bed (LSCFB) riser, where the upwards fluidization takes place, the effects of particle properties on solids holdup are investigated experimentally based on three parameters: superficial liquid velocity, normalized superficial liquid velocity and excess superficial liquid velocity. The results show that the excess superficial liquid velocity (Ul-Ut), among those three parameters, is a more appropriate parameter to evaluate the effects of the particle properties on the solids holdup, facilitating general comparisons for different types of particles. Then such particle property effects are studied analytically by incorporating operating parameters and particle properties into a mathematical model, showing excellent agreement with the experimental results. By this model, the transition velocity demarcating the circulating fluidization regime and the transport regime is determined to complete the flow regime map in liquid-solid fluidization systems. In the Inverse Liquid-Solid Circulating Fluidized Bed (ILSCFB) downer, where the inverse fluidization takes place, under the circulating fluidization regime, the hydrodynamic characteristics are investigated experimentally by the fluidization of Styrofoam and Hollow Glassbeads. For both types of particles, axial solids holdup di stribution is quite uniform, while radial solids holdup distribution is slightly non-uniform with slight increase adjacent to the wall under various operating conditions, but no obvious?core-annulus? structure is observed. Such solids holdup distribution pattern is closely related to the solids circulation rate, superficial liquid velocity, local liquid and particle velocity which are also measured for Styrofoam particles. It is shown that the radial profiles of both liquid and particle velocities are slightly non-uniform, higher at the center region while lower ad jacent to the wall, influenced by solids circulation rate and superficial liquid velocity. The local slip velocity derived from local liquid and particle velocities is found to be very close to the single particle terminal velocity and one-dimensional slip velocity deduced from the superficial liquid, solids velocities and cross-sectional average solids holdup, suggesting that there is no obvious clustering phenomenon and solids segregation in ILSCFB do wner under various operating conditions. The hydrodynamics under the inverse conventional fluidization regime are also studied by examining the bed voidage and dimensionless bed expansion. A new mathematical model correlating Archimedes and Reynolds number is proposed for the prediction of the bed voidage and dimensionless bed expansion in both inverse and upwards liquid-solid fluidization system, exhibiting better accuracy than that of the well known Richardson and Zaki equation. The comparisons of the hydrodynamics in ILSC FB and LSCFB are also made based on the force balance discussion, enabling the compar ison of inverse and upwards circulating fluidization of particles. Then the generalized flow regime map is developed in terms of dimensionless superficial velocity and dime nsionless particle size by determining the demarcations of different flow regimes quantitatively.
Final Report
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Author :
language : en
Publisher:
Release Date : 2007
Final Report written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
Suspensions of solid particles in liquids appear in numerous applications, from environmental settings like river silt, to industrial systems of solids transport and water treatment, and biological flows such as blood flow. Despite their importance, much remains unexplained about these complicated systems. Mucha's research aims to improve understanding of basic properties of suspensions through a program of simulating model interacting particle systems with critical evaluation of proposed continuum equations, in close collaboration with experimentalists. Natural to this approach, the original proposal centered around collaboration with studies already conducted in various experimental groups. However, as was detailed in the 2004 progress report, following the first year of this award, a number of the questions from the original proposal were necessarily redirected towards other specific goals because of changes in the research programs of the proposed experimental collaborators. Nevertheless, the modified project goals and the results that followed from those goals maintain close alignment with the main themes of the original proposal, improving efficient simulation and macroscopic modeling of sedimenting and colloidal suspensions. In particular, the main investigations covered under this award have included: (1) Sedimentation instabilities, including the sedimentation analogue of the Rayleigh-Taylor instability (for heavy, particle-laden fluid over lighter, clear fluid). (2) Ageing dynamics of colloidal suspensions at concentrations above the glass transition, using simplified interactions. (3) Stochastic reconstruction of velocity-field dependence for particle image velocimetry (PIV). (4) Stochastic modeling of the near-wall bias in 'nano-PIV'. (5) Distributed Lagrange multiplier simulation of the 'internal splash' of a particle falling through a stable stratified interface. (6) Fundamental study of velocity fluctuations in sedimentation. (7) Parallelization of Mucha's 'sort-and-sweep' sedimentation code.
Effects Of Particle Properties On Fluidization Characteristics Of Coarse Particles
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Author :
language : en
Publisher:
Release Date : 1993
Effects Of Particle Properties On Fluidization Characteristics Of Coarse Particles written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with categories.
Fluidized-bed reactors can be operated in different flow regimes. Since the gas-solid contacting modes vary as the fluidization regimes change, results obtained from one flow regime for a particulate material can not be applied to another (Grace, 1986). Ascertaining flow regimes of operation is, therefore, essential for design and scaleup of fluidized-bed reactors as well as for reactor performance predictions. During the past decades, considerable research efforts have been spent on flow regime studies for fine particles (Geldart's group A and group B powder). Most of the available data has been obtained with small laboratory-scale units of 15 cm diameter or less. Most fossil energy fluidized bed combustors have used coarse particles as bed material for economic reasons. For example, both bubbling and circulating fluidized bed combustion systems have used coarse coal and limestone particles. It is the objective of this study to better understand the various flow regimes and their transitions from: incipient fluidization to high velocity fluidization using coarse particles in a 30 cm diameter atmospheric fluidized bed cold model. Results of this investigation on high velocity fluidization process will be helpful in predicting operational characteristics and improving circulating fluidized-bed reactor design and scale up for fossil energy applications.
Effects Of Particle Properties On Fluidization Characteristics Of Coarse Particles
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Author : J. S. Mei
language : en
Publisher:
Release Date : 1993
Effects Of Particle Properties On Fluidization Characteristics Of Coarse Particles written by J. S. Mei and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with categories.
Some Effects Of Particle Particle And Particle Fluid Interaction In Two Phase Flow Systems
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Author : R. L. Peskin
language : en
Publisher:
Release Date : 1979
Some Effects Of Particle Particle And Particle Fluid Interaction In Two Phase Flow Systems written by R. L. Peskin and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1979 with categories.