An Investigation on the Mixing Hydrodynamics of a Gas-solid Fluidized Bed PDF Download
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Author: Mario A. Ruvalcaba
Publisher:
ISBN:
Category : Fluidization
Languages : en
Pages :
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Author: Mario A. Ruvalcaba
Publisher:
ISBN:
Category : Fluidization
Languages : en
Pages :
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Author: Md. Rashedul Hasan Sarker
Publisher:
ISBN:
Category : Fluidization
Languages : en
Pages :
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Author: Nicholas P. Cheremisinoff
Publisher: Butterworth-Heinemann
ISBN:
Category : Science
Languages : en
Pages : 888
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
One of the largest challenges for 21st century is to fulfill global energy demand while also reducing detrimental impacts of energy generation and use on the environment. Gasification is a promising technology to meet the requirement of reduced emissions without compromising performance. Coal gasification is not an incinerating process; rather than burning coal completely a partial combustion takes place in the presence of steam and limited amounts of oxygen. In this controlled environment, a chemical reaction takes place to produce a mixture of clean synthetic gas. Gas-solid fluidized bed is one such type of gasification technology. During gasification, the mixing behavior of solid (coal) and gas and their flow patterns can be very complicated to understand. Many attempts have taken place in laboratory scale to understand bed hydrodynamics with spherical particles though in actual applications with coal, the particles are non-spherical. This issue drove the documented attempt presented here to investigate fluidized bed behavior using different ranges of non-spherical particles, as well as spherical. For this investigation, various parameters are controlled that included particle size, bed height, bed diameter and particle shape. Particles ranged from 355 μm to 1180 μm, bed diameter varied from 2 cm to 7 cm, two fluidized beds with diameters of 3.4 cm and 12.4 cm, for the spherical and non-spherical shaped particles that were taken into consideration. Pressure drop was measured with increasing superficial gas velocity. The velocity required in order to start to fluidize the particle is called the minimum fluidization velocity, which is one of the most important parameters to design and optimize within a gas-solid fluidized bed. This minimum fluidization velocity was monitored during investigation while observing variables factors and their effect on this velocity. From our investigation, it has been found that minimum fluidization velocity is independent of bed height for both spherical and non-spherical particles. Further, it decrease with decreasing particle size and decreases with decreasing bed diameter. Shadow sizing, a non-intrusive imaging and diagnostic technology, was also used to visualize flow fields inside fluidized beds for both spherical and non- spherical particles and to detect the particle sizes.
Author: Dimitri Gidaspow
Publisher: Elsevier
ISBN: 0080512267
Category : Science
Languages : en
Pages : 489
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Book Description
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
Author: Rong-Her Jean
Publisher:
ISBN:
Category : Liquids
Languages : en
Pages : 174
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Author: M. M. El-Halwagi
Publisher:
ISBN:
Category : Fluidization
Languages : en
Pages : 286
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Author: Bing Du
Publisher:
ISBN:
Category : Fluidization
Languages : en
Pages :
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Abstract: In this study, the dynamic flow behavior and gas and solids mixing behavior in the turbulent fluidized beds are investigated by using Electrical Capacitance Tomography (ECT) technique and tracer technique. The ECT study reveals that the time-averaged solids holdup distribution exhibits radial symmetry in the turbulent regime. The addition of 10% fine particles decreases the solids concentration in the emulsion phase. The flow behavior in the turbulent fluidized beds is not appreciably affected by the temperature up to 400 oC. More than one spiral motion of bubble swarms is observed in the bubbling regime for the 0.3 m ID fluidized bed. The gas and solids mixing behavior varies significantly with the flow regimes. A small quantity of fine particles is noted to drastically affect the gas and solids mixing behavior in the turbulent fluidized bed. For Group A particles, the flow in the bed transits from the dilute regime to the turbulent regime when the gas velocity is below Utr or the solids circulation rate is lower than Gs, tr. Such flow transition can be signified as the choking transition. For Group B particles, choking is initiated by the formation of the square-nosed slugs (0.05 m ID column) or the wall slugs (0.1 m ID CFB) when the gas velocity is below Utr or the solids circulation rate is lower than Gs, tr. When the gas velocity is above Utr or the solids circulation rate is higher than Gs, tr, choking is characterized by the formation of open slugs. These regime transitions are characterized as the choking transition. A model based on the movement of the solids blob at the center of the bed is developed to predict the critical lifetime of a solids blob in a circulating fluidized bed. The criterion for the occurrence of choking transition in a circulating fluidized bed for both Group A and Group B particles is given.
Author: Oyebanjo Stephen Oke
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Xikui Li
Publisher: Springer
ISBN: 9811019266
Category : Science
Languages : en
Pages : 1414
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Book Description
This book presents the latest advances in Discrete Element Methods (DEM) and technology. It is the proceeding of 7th International Conference on DEM which was held at Dalian University of Technology on August 1 - 4, 2016. The subject of this book are the DEM and related computational techniques such as DDA, FEM/DEM, molecular dynamics, SPH, Meshless methods, etc., which are the main computational methods for modeling discontinua. In comparison to continua which have been already studied for a long time, the research of discontinua is relatively new, but increases dramatically in recent years and has already become an important field. This book will benefit researchers and scientists from the academic fields of physics, engineering and applied mathematics, as well as from industry and national laboratories who are interested in the DEM.
