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Effect Of Operating Conditions And Particle Properties On Electrostatics And Entrainment In Gas Solid Fluidized Beds
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Book Synopsis Effect of Operating Conditions and Particle Properties on Electrostatics and Entrainment in Gas-solid Fluidized Beds by : Turki A. Al-Smari
Download or read book Effect of Operating Conditions and Particle Properties on Electrostatics and Entrainment in Gas-solid Fluidized Beds written by Turki A. Al-Smari and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Effect of Operating Parameters and Particle Properties on Electrostatics in Gas-solid Fluidized Beds by :
Download or read book Effect of Operating Parameters and Particle Properties on Electrostatics in Gas-solid Fluidized Beds written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The influences of operating pressure, temperature and gas velocity on electrostatics in a fluidized bed of glass beads and different grades of polyethylene resin were investigated in a fluidization column of 150 mm inner diameter and 2.0 m height. Eight collision probes at different levels and radial positions measured the electrostatics in the bed. The electrostatics increased as pressure increased, probably due to an increase in bubble rise velocity, frequency and volume fraction. As the pressure increased, particle-particle and particle-wall collisions near the distributor and wall contributed heavily to charge generation. Temperature also played a role. At higher temperatures (up to 90°C), the polarity of net cumulative charge in the bed reversed. As the superficial gas velocity increased, the electrostatics increased. However, at higher gas velocities, the polarity in the freeboard was opposite to that in the bed, indicating that fines entrained from the column carried charges, resulting in a net charge of opposite polarity to that inside the bed. For Geldart group B particles the degree of electrification in the bed slightly increased with decreasing particle size. Charging for group A particles was significantly greater than for group B particles. For binary mixtures of group A and B particles the electrostatics increased as the proportion of small particles increased. As the relative humidity (RH) of fluidizing air increased, the electrostatics decreased. For the RH range (5-30%) explored, the sensitivity of the charging to RH varied significantly depending on the location of the probes. As the proportion of fine glass beads (
Book Synopsis Experimental and Numerical Investigation of Electrostatic Effects in Gas-solid Fluidized Beds by : Youssef Nasro-Allah (docteur en dynamique des fluides).)
Download or read book Experimental and Numerical Investigation of Electrostatic Effects in Gas-solid Fluidized Beds written by Youssef Nasro-Allah (docteur en dynamique des fluides).) and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gas-solid fluidized beds are widely used in industrial processes for energy such as chemical looping combustion, catalytic polymerization, solar receiver, biomass gasification and petroleum refinery. In all these processes, electrostatic forces were usually neglected. In polyolefin industry, the phenomena of electrostatic charges presents a major issues including wall fouling. At a molecular scale, the contact between two particles generates a transfer of electrons/ions, inducing a charge on each particle. As a result, the surrounding gas carries an electric field, resulting in an additional force to the momentum equation known as Lorentz force. The phenomenon depend on many parameters, including materials properties and operating conditions. Several works in literature studied the effect of each parameter. However, there is a lack of research projects which combine both experimental study and theoretical modelling with numerical simulation. Thus, this study falls within the context. It is a part of the Attractivity Chair BIREM (BIological, REacting, Multiphase flows) attributed to Professor Rodney Fox, financially supported by the University of Toulouse, in the framework of the IDEX research program. The project is hosted by the research federation FERMaT. The study aims to combine both experimental study in a lab-scale pilot and the numerical modelling in order to represent the electrostatic force in CFD code through the Euler-Euler formalism. In this work, experiments were performed on different particles size distributions, different materials and different operating conditions. The experimental setup, designed and built during the PhD thesis, consisted of a 1 m height and 0.1 m inner diameter plexiglass column. The measuring technique used for charge is a Faraday cup connected to an electrometer. Results shows two categories of particles: dropped particles that falls immediately after opening the valve and wall particles that stick to the wall. Results show no effect of relative humidity on minimum fluidization velocity (Umf). The evolution of the net charge versus fluidization time showed an exponential trend that reached an equilibrium value for both categories. Wall particles were charged 250 to 450 times than dropped ones. The net charge was decreased by increasing relative humidity. Small particles showed a positive charge whereas all other PSDs were negatively charged. The equilibrium charge of dropped particles did not show significant changes when increasing gas velocity whereas the time needed to reach equilibrium was slightly increased. Wall particles equilibrium charge was significantly increased. On the other hand, the numerical work built an electrostatic model for the Lorentz force in an Eulerian approach. Simulations were carried out with a software called NEPTUNE_CFD. The walls were assumed to be grounded. The model was tested with several test cases. After that, a tribocharging model was developed to take into account the charge generation and transfer. The model was inspired from previous works and transposed into an Eulerian approach. The wall boundary conditions were developed in this study by using less restrictive hypothesis. An estimation of the characteristic times of both charge generation and diffusion was performed, showing that the timescale is very high (several days) and does not match with experimental findings (15 to 20 min). A corrective coefficient was proposed to match with experimental results. Moreover, numerical simulations on a fluidized bed with the same dimensions as the experimental pilot were carried out. In these simulations, the permanent regime was considered. The equilibrium charge was prescribed on the particles. Simulations aimed to compare the no-charge case and the charged case. The effect of the charge on the flow properties were highlighted. These results pointed out the crucial effect of the electrostatic on the gas-particle fluidized suspension.
Book Synopsis Investigation of Operating Parameters Influencing Electrostatic Charge Generation in Gas-solid Fluidized Beds by : Amanda Giffin
Download or read book Investigation of Operating Parameters Influencing Electrostatic Charge Generation in Gas-solid Fluidized Beds written by Amanda Giffin and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrostatic charge generation in gas-solid fluidized beds is a significant industrial problem. Associated problems include particle agglomeration and particle wall fouling. In the polymerization industry this may result in "sheets" of fused polymer, due to exothermic reaction causing the melting of the polymer, which can fall off and block the distributor plate disrupting fluidizing gas flow. Additionally, blockage of the catalyst feed or the polymer removal system can take place or the product can become non-uniform. All of these problems require shut-down of the reactor which results in lost production time. While this phenomena has been identified for many years, the mechanisms involved are not well understood, especially wall fouling and the distribution of charge within the bed. Isolation of individual parameters such as hydrodynamics, operating conditions, and material involved is necessary to evaluate how each parameter impacts charge generation during fluidization. In this thesis, the fluidization system consisted of a stainless steel column, two online Faraday cups, and a retractable distributor plate. This system allowed for the simultaneous measurement of charge within different regions of the bed: the entrained fine particles, the particles adhered to the column wall, and the bulk of the bed. Additionally, mass and particle size distributions were measured and images of the layer of particles adhered to the column wall were taken for comparison. This allowed for a charge distribution comparison and evaluation of wall fouling. Three different parameters were investigated: duration of fluidization, column wall material, and relative humidity of fluidizing gas. Fluidization time was studied for 15, 30, 60, 120, 180, and 360 min; relative humidity was investigated for 0%, 20%, 40%, 60%, and 80% relative humidity. Both fluidization time and relative humidity were evaluated at four different fluidization gas velocities, two each in the bubbling and slugging flow regimes. Column wall material was evaluated for a stainless steel and carbon steel column at two gas velocities, one each in the bubbling and slugging flow regimes. Fluidization time was found to influence wall fouling in the bubbling flow regime as the particle layer continued to build as fluidization progressed. In the slugging flow regime, the particle layer developed within 15 minutes of the onset of fluidization. The bubbling flow regime was shown to have a greater capacity for charge generation than the slugging flow regime. This was due to the vigorous mixing in the bubbling flow regime resulting in more particle-particle interactions. Column wall material was shown to influence wall fouling in the slugging flow regime due to the differences in surface roughness of the columns. This was due to the particle-wall contacts resulting in frictional charging which is the predominant charging mechanism in this flow regime. Charge was also impacted in the bubbling flow regime in those particles that were adhered to the column wall. Relative humidity was found to influence wall fouling at the lowest gas velocity tested. However, variations in generation of charge occurred at all fluidization gas velocities tested; the charge-to-mass ratios for the particles adhered to the column wall in the slugging flow regime decreased with high relative humidities. This was due to either the formation of a water film layer on the column wall or instantaneous surface water films on the particles throughout fluidization.
Book Synopsis Fluid Dynamics of Turbulent Fluidized Beds for Geldart’s Group B Particles by : Tom Wytrwat
Download or read book Fluid Dynamics of Turbulent Fluidized Beds for Geldart’s Group B Particles written by Tom Wytrwat and published by Cuvillier Verlag. This book was released on 2022-02-15 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: An in-depth experimental study of the fluid dynamics of turbulent fluidized beds with particles of Geldart’s Group B was carried out. For this purpose, fluidization behavior was investigated in different fluidized bed plants having diameters in the range of 0.05 m to 1 m. Pressure fluctuation analysis has been used as an identification tool for the turbulent fluidized bed regime. Different fluidization conditions have been investigated by variation of the fluidized bed properties, the bed material properties, and the gas properties. Based on the measured data, a correlation predicting the transition velocity from bubbling to turbulent fluidization is introduced. To investigate the local flow structure, capacitance probe measurements have been carried out. Using this measurement technique, local solids concentrations and properties of rising bubbles have been determined and analyzed. Finally, an empiric fluid dynamic model was developed using the local measurement data. It is mainly based on capacitance probe measurements and shows high accuracy in comparison to pressure data.
Book Synopsis Study of Electrostatic Charging and Particle Wall Fouling in a Pilot-scale Pressurized Gas-Solid Fluidized Bed Up to Turbulent Flow Regime by : Di Song
Download or read book Study of Electrostatic Charging and Particle Wall Fouling in a Pilot-scale Pressurized Gas-Solid Fluidized Bed Up to Turbulent Flow Regime written by Di Song and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In gas-solid fluidized beds, the generation of electrostatic charges due to continuous contacts between fluidizing particles, and the particles and the fluidization vessel wall, is unavoidable. Industrial operations, such as the production of polyethylene, are susceptible to significant operational challenges caused by electrostatics including reactor wall fouling, a problem known as "sheeting". The formation of particle sheets can require shutdown periods for clean-up which results in significant economic losses. To gain a better understanding of the underlying mechanisms of electrostatic charging in gas-solid fluidized beds, in an attempt to eliminate or minimize this problem, a pilot-scale pressurized gas-solid fluidization system was designed and built, housing an online electrostatic charge measurement technique consisting of two Faraday cups. The system permits the study of the degree of particle wall fouling at pressures and temperatures up to 2600 kPa and 100°C, respectively, and gas velocities up to 1 m/s (covering a range including turbulent flow regime). The system also allowed, for the first time, the measurement of the fluidizing particles' mass, net charge and size distribution in various regions of the bed, especially those related to the wall coating under the industrially relevant operating conditions of high pressures and gas velocities. Experimental trials were carried out using polyethylene resin received from commercial reactors to investigate the influence of pressure and gas velocity on the bed hydrodynamics and in turn, the degree of bed electrification. Mechanisms for particle charging, migration and adherence to the column wall were proposed. The size distribution of the gas bubbles shifted towards smaller bubbles as the operating pressure was raised. Thus, higher pressures lead to greater mixing within the bulk of the bed and resulted in a higher degree of particle wall fouling. Moreover, the extent of wall fouling increased linearly with the increase in gas velocity and as the bed transitioned to turbulent regime, due to the increase in particle-wall contacts. Bipolar charging was observed especially within the wall coating with smaller particles being negatively charged. Overall, particle-wall contacts generated negatively charged particles resulting in a net negative charge in the bed, whereas particle-particle contacts generated positively and negatively charged particles resulting in no net charge when entrainment was negligible. The formation of the wall layer and its extent was influenced by the gravitational and drag forces balancing the image force and Coulomb forces (created by the net charge of the bed and the metallic column wall as the attraction between oppositely charged particles).
Book Synopsis Circulating Fluidized Beds by : J.R. Grace
Download or read book Circulating Fluidized Beds written by J.R. Grace and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 599 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the late 1970s there has been an explosion of industrial and academic interest in circulating fluidized beds. In part, the attention has arisen due to the environmental advantages associated with CFB (circulating . fluidized bed) combustion systems, the incorporation of riser reactors employing cir culating fluidized bed technology in petroleum refineries for fluid catalytic cracking and, to a lesser extent, the successes of CFB technology for calcina tion reactions and Fischer-Tropsch synthesis. In part, it was also the case that too much attention had been devoted to bubbling fluidized beds and it was time to move on to more complex and more advantageous regime,S of operation. Since 1980 a number of CFB processes have been commercialized. There have been five successful International Circulating Fluidized Bed Confer ences beginning in 1985, the most recent taking place in Beijing in May 1996. In addition, we have witnessed a host of other papers on CFB funda mentals and applications in journals and other archival publications. There have also been several review papers and books on specific CFB topics. However, there has been no comprehensive book reviewing the field and attempting to provide an overview of both fundamentals and applications. The purpose of this book is to fill this vacuum.
Book Synopsis The Effect of Particle Size on the Properties of Gas-fluidized Beds by : K. S. Sutherland
Download or read book The Effect of Particle Size on the Properties of Gas-fluidized Beds written by K. S. Sutherland and published by . This book was released on 1964 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of a continuous method for determining changes in particle size and particle size distribution in fluid-bed systems has been studied experimentally. Differential pressure measurements were employed to study the effects of solid particle size on the behavior of gas-fluidized beds. The relevant bed properties are briefly described and a review given of previous work on the study of fluidized-bed quality. It is shown that, within certain limitations, measurements of bed quality can be used to indicate changes in particle size. Gas-bubble velocities, while increasing in proportion to the square root of bubble diameter, are also shown to be dependent on particle size, increasing as the particle size decreases.
Book Synopsis Circulating Fluidized Bed Technology II by : Prabir Basu
Download or read book Circulating Fluidized Bed Technology II written by Prabir Basu and published by Pergamon. This book was released on 1988 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: Circulating Fluidized Bed Technology II is a result of a series of science-related conferences in the 1980s. The text contains various studies, facts, and discussions on fluidized beds. The book begins by going through the rise and fall of circulating systems, specifically fluid dynamics. The chapter continues with a wider discussion of hydrodynamics, which includes its scales, particles, and different math formulas. In the several chapters that follow, a thorough study of fluidized beds and its subtopics are presented, which include particle behavior, combustion, heat transfer process, reactors, gas mixing, parameters, measurements, and characteristics. The variations of fluidized beds, including the multisolid, dual-column, and turbulent, are also given. The book serves as a very useful reference for undergraduates and postgraduates of physics, chemistry, and other related fields.
Book Synopsis Circulating Fluidized Bed Technology II by : Prabir Basu
Download or read book Circulating Fluidized Bed Technology II written by Prabir Basu and published by Pergamon. This book was released on 1988 with total page 602 pages. Available in PDF, EPUB and Kindle. Book excerpt: Circulating Fluidized Bed Technology II is a result of a series of science-related conferences in the 1980s. The text contains various studies, facts, and discussions on fluidized beds. The book begins by going through the rise and fall of circulating systems, specifically fluid dynamics. The chapter continues with a wider discussion of hydrodynamics, which includes its scales, particles, and different math formulas. In the several chapters that follow, a thorough study of fluidized beds and its subtopics are presented, which include particle behavior, combustion, heat transfer process, reactors, gas mixing, parameters, measurements, and characteristics. The variations of fluidized beds, including the multisolid, dual-column, and turbulent, are also given. The book serves as a very useful reference for undergraduates and postgraduates of physics, chemistry, and other related fields.
Book Synopsis Circulating Fluidized Bed Technology by : P. Basu
Download or read book Circulating Fluidized Bed Technology written by P. Basu and published by Elsevier. This book was released on 2013-10-22 with total page 465 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume focuses on the present status of circulating fluidized bed technology and provides design information not available elsewhere. Areas covered include combustion of fossil fuel, hydrodynamics, combustion and environmental pollution, design and operating experiences, heat transfer and hydrodynamics, and process applications.
Book Synopsis Circulating Fluidized Bed Technology by : Prabir Basu
Download or read book Circulating Fluidized Bed Technology written by Prabir Basu and published by Elsevier. This book was released on 2013-10-22 with total page 591 pages. Available in PDF, EPUB and Kindle. Book excerpt: Circulating Fluidized Bed Technology II is a result of a series of science-related conferences in the 1980s. The text contains various studies, facts, and discussions on fluidized beds. The book begins by going through the rise and fall of circulating systems, specifically fluid dynamics. The chapter continues with a wider discussion of hydrodynamics, which includes its scales, particles, and different math formulas. In the several chapters that follow, a thorough study of fluidized beds and its subtopics are presented, which include particle behavior, combustion, heat transfer process, reactors, gas mixing, parameters, measurements, and characteristics. The variations of fluidized beds, including the multisolid, dual-column, and turbulent, are also given. The book serves as a very useful reference for undergraduates and postgraduates of physics, chemistry, and other related fields.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1961 with total page 808 pages. Available in PDF, EPUB and Kindle. Book excerpt: NSA is a comprehensive collection of international nuclear science and technology literature for the period 1948 through 1976, pre-dating the prestigious INIS database, which began in 1970. NSA existed as a printed product (Volumes 1-33) initially, created by DOE's predecessor, the U.S. Atomic Energy Commission (AEC). NSA includes citations to scientific and technical reports from the AEC, the U.S. Energy Research and Development Administration and its contractors, plus other agencies and international organizations, universities, and industrial and research organizations. References to books, conference proceedings, papers, patents, dissertations, engineering drawings, and journal articles from worldwide sources are also included. Abstracts and full text are provided if available.
Book Synopsis Essentials of Fluidization Technology by : John R. Grace
Download or read book Essentials of Fluidization Technology written by John R. Grace and published by John Wiley & Sons. This book was released on 2020-06-15 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt: A concise and clear treatment of the fundamentals of fluidization, with a view to its applications in the process and energy industries.
Book Synopsis Fluidized-Bed Reactors: Processes and Operating Conditions by : John G. Yates
Download or read book Fluidized-Bed Reactors: Processes and Operating Conditions written by John G. Yates and published by Springer. This book was released on 2016-09-27 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Fluid Dynamics of Turbulent Fluidized Beds for Geldart's Group B Particles by : Tom Wytrwat
Download or read book Fluid Dynamics of Turbulent Fluidized Beds for Geldart's Group B Particles written by Tom Wytrwat and published by SPE-Schriftenreihe 20. This book was released on 2022-02-15 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: An in-depth experimental study of the fluid dynamics of turbulent fluidized beds with particles of Geldart's Group B was carried out. For this purpose, fluidization behavior was investigated in different fluidized bed plants having diameters in the range of 0.05 m to 1 m. Pressure fluctuation analysis has been used as an identification tool for the turbulent fluidized bed regime. Different fluidization conditions have been investigated by variation of the fluidized bed properties, the bed material properties, and the gas properties. Based on the measured data, a correlation predicting the transition velocity from bubbling to turbulent fluidization is introduced. To investigate the local flow structure, capacitance probe measurements have been carried out. Using this measurement technique, local solids concentrations and properties of rising bubbles have been determined and analyzed. Finally, an empiric fluid dynamic model was developed using the local measurement data. It is mainly based on capacitance probe measurements and shows high accuracy in comparison to pressure data.
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1989 with total page 744 pages. Available in PDF, EPUB and Kindle. Book excerpt:
