Engineering Commons^™

An Analysis Of Pressure Fluctuations In A Cfb Of Heavy Minerals, Adam Luckos, Quinn G. Reynolds , Paul Den Hoed

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Pressure fluctuations were measured at high frequencies in a CFB model operated with air at ambient conditions. The model comprises an 80-mm-ID, 5-m-tall riser with a blind-T exit, a cyclone, a 50-mm-ID standpipe, and an L-valve. Tests were conducted with particles of natural rutile (TiO2), a heavy mineral mined from coastal dunes. The particles fall into group B of Geldart’s classification. The solids inventory was kept at 25 kg. The superficial gas velocity ranged from 3 to 6 m/s. The solid circulation flux varied between 10 and 40 kg/m2.s.

Profiles of solid concentrations in the riser are C-shaped. The amplitude …

Title Page - Table Of Contents - Preface - List Of Reviewers, Xiaotao T. Bi, Franco Berruti, Todd S. Pugsley

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

No abstract provided.

Improved Standpipe Entrance For Stable High-Flux Flow, D. Rusnell, John R. Grace, Xiaotao T. Bi, C. Jim Lim, P. Ronan, C. A. Mcknight

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Cold model tests were used to show the causes of instabilities in the operation of the standpipe entrance (“sore thumb”) in industrial scale fluid cokers. New geometries were tested which might provide higher flows and prevent operating problems such as flow reversals and flooding, while also minimizing the adverse effects of fouling. The tests were conducted using FCC particles in a geometrically and dynamically scaled half-column of approximately 1/9th scale which had previously been used to show the effects of baffles on fluid coker strippers. The addition of sloping surfaces to increase the surface area for ingress of particles was …

Hydrodynamic Scale-Up Of Circulating Fluidized Beds, Ted Knowlton, S. B. Reddy Karri, J. S. Smith

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

A general procedure that can be used to scale up circulating fluidized beds is presented. It consists of developing a mathematical model in conjunction with measuring 1) the radial dispersion coefficient (Dr) using gas tracers, 2) the radial solids velocity profile using a Pitot tube and 3) the radial distribution of solids density (1 - ε) using an optical probe. If the resulting information is obtained in a riser 200 mm or greater in diameter, it can be used in conjunction with the mathematical model for scale-up.

Subject Index, Xiaotao T. Bi, Franco Berruti, Todd S. Pugsley

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

No abstract provided.

Measuring The Gas-Solids Distribution In Fluidized Beds - A Review, J. Ruud Van Ommen, Robert F. Mudde

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

This paper reviews techniques for measuring the voidage distribution in gas-solid fluidized beds, with a focus on the developments during the last ten years. Most attention is given to recent progress in tomography and pressure measurements, but visual observations, capacitance probes and optical probes are also covered.

Presentation Slides: Hydrodynamic Scale-Up Of Circulating Fluidized Beds, Ted Knowlton

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

No abstract provided.

Analytical Multi-Scale Methodology For Fluidization Systems - Retrospect And Prospect, Jinghai Li, Wei Ge, Jiayuan Zhang, Shiqiu Gao, Wei Wang, Ning Yang, Qicheng Sun, Jian Gao

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Understanding the spatio-temporal multi-scale structure of fluidization is a challenging problem. This presentation reviews our 20-year efforts on this subject, showing the roadmap that has gradually evolved from a simple idea to a systematic methodology inclusive of subsidiary, related systems and industrial applications. The strategy of establishing stability conditions through analyses of the compromise between dominant mechanisms is emphasized. The presentation concludes with prospects for further theoretical explorations and industrial applications.

Presentation Slides: Analytical Multi-Scale Methodology For Fluidization Systems - Retrospect And Prospect, Jinghai Li

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

No abstract provided.

Presentation Slides: Fluidized Bed Combustion For Clean Energy, Filip Johnsson

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

No abstract provided.

Presentation Slides: Measuring The Gas-Solids Distribution In Fluidized Beds - A Review, J. Ruud Van Ommen

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

No abstract provided.

Fluidized Bed Combustion For Clean Energy, Filip Johnsson

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

This paper gives a brief overview of the status and prospects for fluidized bed combustion (FBC) for clean energy, with focus on power and heat generation. The paper summarizes recent development trends for the FB technology and makes an outlook into the future with respect to challenges and opportunities for the technology. The paper also identifies areas related to fluidization, which are critical for the technology and, thus, will require research. The main advantage with the FBC technology is the fuel flexibility. A compilation of 715 FB boilers (bubbling and circulating) worldwide illustrates the two main applications for the FBC …

Solids Flux, Velocity And Local Solid Fraction Measurements In A Cfb Riser, Ronald W. Breault, Christopher Guenther

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

In this investigation a fiber-optic probe and an extraction solids probe are used to measure particle velocities and solids flux values. These are subsequently used to determine the local solids fractions as a function of radial position in a cold flow circulating fluidized bed (CFCFB) in operation at the National Energy Technology Laboratory (NETL). Measurements were taken under several separate operating conditions ranging from dilute up-flow to core-annular flow to fast fluidization using nominal 800 micron cork particles. The solids properties and test operating conditions were chosen particularly to provide dynamic similitude between the test data and the operation of …

Analysis Of Heat Transfer Between Two Particles For Dem Simulations, Kenya Kuwagi, Muhammad Arif Bin Mokhtar, Toshihiro Takami, Masayuki Horio

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The purpose of the present study was to develop a model of heat transfer between particles that can be incorporated into the discrete element method (DEM). The flow around a particle was measured by particle imaging velocimetry (PIV) and the temperature of the particle was measured using a thermocouple and an infrared camera. The experimental data of heat transfer were classified according to the heat transfer mechanism, namely convection, conduction and contact. These values for heat transfer were compared with those calculated using previously derived estimation equations. From these results, we adopted the thermal contact resistance model, which is related …

Numerical Investigation Of The Layer-Inversion Phenomenon In Binary Solid Liquid Fluidized Beds, Kevin F. Malone, Bao H. Xu, Michael Fairweather

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Layer inversion behaviour in binary-solid liquid fluidized beds is examined using a Combined Continuum and Discrete Model. A suitable bidisperse system was selected from information in the literature. By simulating the fluidization of the system at a range of liquid velocities, varying degrees of segregation and mixing have been observed.

Flow Characteristics Of Fully Wetted Binary Solid Mixtures In Gas Fluidized Beds With Inclined Gas Distributors, Yusumi Nagahashi, John R. Grace, Norman Epstein, Yutaka Asako, Akira Yokogawa

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

A unique gas-fluidized bed in which fluidization is enhanced by adding a little water has potential for soft abrasive washing of various products. Preliminary experiments were carried out for the washing of farm products. Gas fluidized beds of binary solids mixtures with inclined gas distributors provide hydrodynamic and mixing data assisting the design of dry and wet gas-fluidized beds.

Mechanistic Study Of Nano-Particle Fluidization, X. S. Wang, F. Rahman, Martin J Rhodes

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Degussa Aerosil R974 powder, with a primary particle size of 12 nm, was fluidized using nitrogen in a cylindrical vessel, 50-mm-id and 900 mm in height. Characteristics of incipient fluidization are analysed in relation to variations in the initial packing conditions. Bed collapse experiments were performed and the results are used for assessing fluidization characteristics of the particles. It was found that nanoparticles exhibit characteristics of both Group A and Group C powders. Various methods for estimating the cohesion forces between nanoparticle aggregates are discussed.

Hydrodynamic Effects Of Particle Chaining In Liquid-Solid Magnetofluidized Beds, Carlos F. Cruz-Fierro, Brian P. Reed, Joaquin Pinto-Espinoza, Goran N. Jovanovic

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

In a fluidized bed of magnetically susceptible particles, the presence of a magnetic field induces particle chaining due to interparticle magnetic forces. The particle chains offer less resistance to flow, resulting in a decrease of the drag coefficient. The change in drag coefficient as a function of hydrodynamic and magnetic operating conditions of a liquid-solid magnetofluidized bed is studied.

Multiple Particle Tracking In A Fluidised Bed, A. Ingram, Z. Yang, S. Bakalis, D. J. Parker, X. Fan, P. J. Fryer, J. P.K. Seville

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Positron Emission Particle Tracking (PEPT) is a versatile method for following the motion of a single radioactive tracer particle in a fluidised bed. However, there are many applications in which it would be useful to be able to follow the motion of two or more particles simultaneously in cooperative motion. The tracers are labelled with different intensities of radiation and located by converging sequentially on centres of activity. Two 600&#;m polyethylene particles have been followed in a 15 cm diameter bed and their contact events studied.

Detection Of Oversized Material In A Hydrotransport Slurry Pipe Using Non-Invasive Acoustic Method, Katherine Albion, Joesph Downey, Erin Hansuld, Derek Hartling, Lauren Briens, Franco Berruti, Steven Mcdougall

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Large material, such as rocks, in a hydrotransport system of fine particles can damage pumps and equipment. A reliable, non-intrusive, and on-line acoustic method was developed for the detection of this large material. Analysis of signals recorded by microphones attached to the pipe wall allows for the reliable detection of rocks of different sizes and shapes, with no false positives.

Tapered Fluidized Beds And The Role Of Fluidization In Mineral Emplacement, Thomas M. Gernon, Mark A. Gilbertson, R. Stephen J. Sparks, Matthew Field

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

One of the most prominent features of fluidized beds is their ability to mix and segregate. This is of great importance for many industrial processes, but takes on a particular significance for mineral extraction where a small amount of valuable matter is mixed with a large amount of waste. In this study we consider the occurrence of diamonds in the volcanic rock called “kimberlite”. These are often emplaced (erupted and deposited) in large volcanic pipes commonly referred to as “diatremes” (length scale of the order of a kilometre) with a vent at the bottom through which the minerals were introduced …

A Dem Study Of Geldart Group A Particle Bed Fluidisation Behavior Across The Regimes, Fang Yang, David K. Kafui, C. Thornton, J.P.K. Seville

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The objective of the study is to identify the transitions in bed behavior as the gas velocity is increased to cover the complete range from minimum fluidization through bubbling and turbulent behavior to pneumatic transport. The simulation data is examined in terms of computer visualizations, the rate of change of average bed voidage and pressure drop fluctuations.

Improving The Conversion In Fluidised Beds With Secondary Injection, Dana Christensen, John Nijenhuis, J. Ruud Van Ommen, Marc-Oliver Coppens

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The effect of secondary injection on the performance of a fluidised bed reactor has been studied. A modified Kunii and Levenspiel model was used to predict the effect on conversion and indicates that the reduction in bubble size caused by secondary injection results in a significant increase. This effect was confirmed experimentally, although the model appears to underestimate the experimental values.

Gas-Solid Structure In The Vicinity Of A Sparger Nozzle In A Fluidized Bed, Pierre Sauriol, Heping Cui, Jamal Chaouki

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

An experimental approach is proposed to investigate the gas-solid structure in the vicinity of a sparger nozzle in a fluidized bed. The local hydrodynamics were studied under injection velocities ranging between 0 and 100 m/s and three orientations. A fiber-optic probe was used to measure the instantaneous local particle holdup near the tip of the sparger nozzle. Under the investigated conditions, the local gas-solid structure was influenced on the measurement position, nozzle orientation and injection velocity. Four distinct zones were identified from the local particle holdup data, with the boundaries corresponding to characteristic jet lengths. Strong discrepancies were found with …

Self-Fluidization Of Fastly-Moving Granular Gravity Currents With Implication On Pyroclastic Flows, Piero Bareschino, Antonio Marzocchella, Piero Salatino, Teresita Gravina, Lucio Lirer, Paola Petrosino

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The fast motion of gravity currents of group A granular solids is studied with a focus on the dynamical structure of the frontal zone. The frontal zone of the current is “immobilized” and observed in a fixed frame of reference by letting the current flow inside a rotary drum, big enough to make curvature effects negligible. The establishment of a variety of flow regimes, including intermittent avalanching, periodic “plunging breaking” and permanent fluidization of the granular solids in the frontal zone, can be related to flow conditions and to the nature of the granular solids.

H2-Rich Syngas From Renewable Sources By Dual Fluidized Bed Steam Gasification Of Solid Biomass, Christoph Pfeifer, Tobias Pröll, Bernhard Puchner, Hermann Hofbauer

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Steam gasification of solid biomass yields high quality producer gases that can be used for efficient combined heat and power production (CHP) and as a renewable resource for chemical syntheses. The dual fluidized bed steam gasification technology provides the necessary heat for steam gasification by circulating hot bed material that is heated in a second fluidized bed reactor by combustion of residual biomass char. The hydrogen content in producer gas of such gasifiers is about 40 vol% (dry basis). Addition of carbonates to the bed material and adequate adjustment of operation temperatures in the reactors allow selective transport of CO2 …

Fluid-Dynamic Investigations In A Cold Model For A Dual Fluidized Bed Biomass Steam Gasification Process: Optimization Of The Cyclone, Andreas Kreuzeder, Christoph Pfeifer, Hermann Hofbauer

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Gasification of biomass is an attractive technology for combined heat and power production. Although a great deal of research and development work has been carried out during the past decade the commercial breakthrough for this technology is still not in sight. The optimisation of the operation costs influences significantly the economic efficiency. Especially bed material consumption constitutes a major part of expenses in fluidised bed systems. Thus, cyclones for circulating fluidized beds need to be designed properly. A dual fluidized bed steam gasifier is in commercial operation at the biomass CHP (combined heat and power plant) in Güssing, Austria since …

Combustion Studies Of Sawdust In A Bubbling Fluidized Bed, K.V.N. Srinivasa Rao

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Biomass fuels are difficult to handle due to high moisture and fines content. In the present work, the effect of secondary air injection on combustion efficiency of sawdust in the fluidized bed combustor has been discussed. An enlarged disengagement section is provided to improve combustion of fines. The maximum possible combustion efficiency with saw dust is 99.2 % and is observed at 65 % excess air.

Authors Index, Xiaotao T. Bi, Franco Berruti, Todd S. Pugsley

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

No abstract provided.

Kinetics Of Surface-Initiated Photoiniferter-Mediated Photopolymerization And Synthesis Of Stimuli-Responsive Polymer Brushes, Santosh Rahane

All Dissertations

The focus of this research is to understand the kinetic and mechanistic aspects of surface-initiated photoiniferter-mediated photopolymerization (SI-PMP) and exploit the robustness of SI-PMP to synthesize stimuli-responsive polymer brushes. The 'living' characteristics of dithiocarbamate-based photoiniferter-mediated photopolymerization are well documented. However, in this dissertation I show that the growth of poly(methyl methacrylate) (PMMA) brushes by SI-PMP is nonlinear, suggesting loss of radicals during SI-PMP and, in turn, non-living characteristics. Results from kinetic models in conjunction with experimental results suggest that irreversible bimolecular termination reactions are a primary culprit for the loss of radicals during SI-PMP. To overcome this problem of irreversible …