Hydrodynamics and Flow Structure, Gas and Solids Mixing Behavior, and Choking Phenomena in Gas-solid Fluidization PDF Download
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Author: Bing Du
Publisher:
ISBN:
Category : Fluidization
Languages : en
Pages :
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Book Description
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: Bing Du
Publisher:
ISBN:
Category : Fluidization
Languages : en
Pages :
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Book Description
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: Nicholas P. Cheremisinoff
Publisher: Butterworth-Heinemann
ISBN:
Category : Science
Languages : en
Pages : 888
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Book Description
Author: Liang-Shih Fan
Publisher: Butterworth-Heinemann
ISBN: 1483289516
Category : Technology & Engineering
Languages : en
Pages : 784
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Book Description
This book provides a comprehensive mechanistic interpretation of the transport phenomena involved in various basic modes of gas-liquid-solid fluidization. These modes include, for example, those for three-phase fluidized beds, slurry columns, turbulent contact absorbers, and three-phase fluidized beds, slurry columns, turbulent contact absorbers, and three-phase transport. It summarizes the empirical correlations useful for predicting transport properties for each mode of of operation.Gas-Liquid-Solid Fluidization Engineering provides a comprehensive account of the state-of-the-art applications of the three-phase fluidization systems that are important in both small-and large-scale operations. These applications include fermentation,biological wastewater treatment, flue gas desulfurization and particulates removal, and resid hydrotreating. This book highlights the industrial implications of these applications. In addition, it discusses information gaps and future directions forresearch in this field.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 858
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Book Description
Author: Nicholas P. Cheremisinoff
Publisher:
ISBN: 9780608015798
Category :
Languages : en
Pages : 880
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Book Description
Author: Wai Man R. Lau
Publisher:
ISBN:
Category : Fluidization
Languages : en
Pages :
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Book Description
Abstract: Slurry bubble columns and gas-solid fluidized bed reactors are some of the most commonly used industrial processes. Considerable interests have been recognized in the field of physical, chemical, petrochemical, electrochemical, and biochemical operations (Fan, 1989). In these reactor systems, large axial dispersion of phases and high flow patterns can be achieved by the excellent macromixing characteristics. It also provides excellent heat and mass transfer without the aid of external mechanisms and relatively easy operation. Despite the advantages of operations, the transport behavior in these systems is very complex and a comprehensive knowledge of the hydrodynamics, heat and mass transfer and mixing are required for successful application of these systems. Some aspects of the fundamental characteristics of evaporative liquid jets in gas-liquid-solid flows are studied and some pertinent literature is reviewed. It is found that the injection of an evaporative liquid jet decreases the minimum fluidization velocity at a high pressure due to the additional gas flow generated from liquid evaporation. Fluidizing gas velocities have no significant effect on the jet penetration length in a dense phase fluidized bed while it reduces the radial dispersed distance of the evaporative liquid. The tomographic images of liquid nitrogen injection in a dense phase fluidized bed indicate a distribution of reduced bubble sizes compared to a dry bed. The hydrodynamics, gas-liquid mass transfer properties and liquid entrainment phenomena in a high pressure and high temperature bubble column is investigated. Effects of pressure on hydrodynamics and mass transfer properties are mainly through the change in gas and liquid physical properties, which in turn changes the bubble dynamics that govern the transport phenomena. Experimental results show that liquid velocities have a direct influence on kl while other factors have a dominant effect on the interfacial area over kl. Liquid entrainment in bubble columns is controlled by the droplet formation during bubble bursting at interface. Effect of pressure on liquid entrainment is to due to the higher drag force exerted on the liquid droplet with higher gas density and the formation of smaller droplet by the smaller bubbles at high pressure.
Author:
Publisher: 清华大学出版社有限公司
ISBN: 9787302125068
Category : Fluidized reactors
Languages : en
Pages : 452
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Book Description
本书介绍了流态化科学与工程方面的研究进展,与多相反应工程和工艺相关的粉体、造粒、绿色化工和生态工业等前沿领域的新内容和新进展,以及能源与环境等涉及可持续发展的战略问题。
Author: Liang-Shih Fan
Publisher: Cambridge University Press
ISBN: 9780521021166
Category : Technology & Engineering
Languages : en
Pages : 576
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Book Description
Gas-solid flows are involved in numerous industrial processes and occur in various natural phenomena. This authoritative book addresses the fundamental principles that govern gas-solid flows and the application of these principles to various gas-solid flow systems. The book is arranged in two parts: Part I deals with basic relationships and phenomena, including particle size and properties, collision mechanics, momentum transfer, heat and mass transfer, basic equations, and intrinsic phenomena in gas-solid flows. Part II discusses gas-solid flow systems of industrial interest such as gas-solid separators, hoppers and standpipes, dense-phase fluidized beds, fluidized beds, pneumatic conveying systems, and heat and mass transfer in fluidization systems. As a comprehensive text on gas-solid flows, which includes end-of-chapter problems, this book is aimed at students, but will also be useful to a broad range of engineers and applied scientists. Solutions manual available.
Author: Rong-Her Jean
Publisher:
ISBN:
Category : Liquids
Languages : en
Pages : 174
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Book Description
Author: American Chemical Society. Committee on Professional Training
Publisher:
ISBN:
Category : Biochemistry
Languages : en
Pages : 1932
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Book Description
Faculties, publications and doctoral theses in departments or divisions of chemistry, chemical engineering, biochemistry and pharmaceutical and/or medicinal chemistry at universities in the United States and Canada.
