Engineering Commons^™

Force On A Large Sphere Immersed In An Expanded Water-Fluidized Bed Over A Wide Range Of Voidage Values, Alberto Di Renzo, Nicola Grassano, Francesco P. Di Maio

Fluidization XV

The presence of large objects immersed in a fluidized bed has been long studied in order to verify to what extent can the analogy with a buoyant body in a liquid represent the object-to-suspension interaction (1). One of the most useful information resulting from such study is the effective drag force exerted on the object and how it is related to the suspension properties, particularly with respect to the expansion degree. Implications are found also in the formulation of drag force expressions for homogeneous polydisperse systems.

In the present work an experimental series of tests has been conducted on a …

Solids Maldistribution In Parallel Cyclones, T. M. Knowlton, John Findlay, Larry P. Hackman, Craig A. Mcknight

Fluidization XV

The amount of solids maldistribution in parallel cyclones was investigated to determine what parameters affected the maldistribution. In many fluidized bed processes with parallel cyclones (as many as 20 in parallel in some cases), it has been noted that unequal erosion (wear) can occur in the cyclones. This results in very short run lengths in order to repair the cyclones with the most wear. This unequal wear has been attributed to unequal solids distribution to the cyclones. In addition to the increased wear, cyclone efficiencies are affected as well.

In the specific concern that generated this study, it was found …

Improved Gas-Solid Mixing And Mass Transfer In A Pulsed Fluidized Bed Of Biomass With Tapered Bottom, Dening Jia, C. Jim Lim, Xiaotao Bi, Shahab Sokhansanj, Atsushi Tsutsumi

Fluidization XV

To improve fluidization quality and mass transfer rate of biomass fluidized beds with pulsed gas flow, an existing fluidized bed with rectangular cross-section area was modified with the insertion of a tapered bottom section such that dead zones observed in the original design could be eliminated. Batch drying tests were performed as an indirect indicator of gas-solid contact efficiency and mass transfer performance. Compared to the original design, biomass particles could be fluidized at a wider range of gas pulsation frequencies with significantly reduced channeling and gas bypassing in the new tapered design. Faster drying and thus improved mass transfer …

Cfd-Dem Simulation Of Nanoparticle Agglomerates Fluidization With A Micro- Jet, Daoyin Liu, Berend G. M. Van Wachem, J. Ruud Van Ommen, Robert F. Mudde, Xiaoping Chen

Fluidization XV

Nanoparticles can be fluidized as agglomerates, but for some materials this is cumbersome due to the cohesive nature. Micro-jets are shown to be effective for improving the fluidization in such cases (1). In this study, the mechanisms of micro-jet assistance are investigated by using an adhesive CFD-DEM (Computational Fluid Dynamics – Discrete Element Modelling) model. In previous studies, the complex agglomerates found in a fluidized bed are treated as the discrete elements (2). Here we use the simple agglomerates as the discrete elements, which are the building blocks of the larger complex agglomerates. The collision of the simple agglomerates are …

Segregation Of Equal-Sized Particles Of Different Densities In A Vertically Vibrated Fluidized Bed, E. Cano-Pleite, A. Acosta-Iborra, F. Hernández-Jiménez, T. Tsuji, C. R. Müller

Fluidization XV

Many operations in the chemical and energy-conversion industries rely on the fluidization of heterogeneous materials. During fluidization, particles of different densities can segregate, even if they are of the same size. Segregation is typically an undesired phenomenon, especially in fluidized bed reactors (1). Thus, an understanding of segregation on a fundamental level is paramount to identify effective measures to control it. One approach to control segregation could be the vibration of the bed vessel. However, there is very little literature available concerning the effect of vibration on density-induced segregation dynamics (2).

Thus, this work studies the influence of vibration on …

Reversal Of Gulf Stream Circulation In A Vertically Vibrated Triangular Fluidized Bed, E. Cano-Pleite, A. Acosta-Iborra, F. Hernández-Jiménez, C. R. Müller

Fluidization XV

Vibrated fluidized beds are a process intensification technique consisting in introducing vibratory kinetic energy in a fluidized bed (1). In this work we assess experimentally the effect of vibration on the gulf-stream circulation pattern of particles in a fluidized bed that is of triangular shape. The bed has 0.206 m span and 0.01 m thickness. The base of the bed is composed of two inclined walls, each one forming an angle of 45º with the horizontal. Air was injected through the inclined bed walls to fluidize the bed (see Figure 1a). This gas injection, together with vibration, can make the …

Experimental Validation Of Cfd Hydrodynamic Models For Catalytic Fast Pyrolysis (Cfp), Bruce D Adkins, Travis Dudley, Neeti Kapur, Peter Blaser, James Parker

Fluidization XV

Catalytic Fast Pyrolysis (CFP) is a means of producing renewable fuels and chemicals from lignocellulosic biomass. KiOR, a world leader in this area, has developed a CFP technology along the lines of the FCC process.

In early 2015, KiOR engaged with CPFD Software to develop a new, parallel path for developing and optimizing its CFP technology. Emphasis was placed on hydrodynamics predictions, since that is one key area where KiOR’s CFP differs significantly from FCC. The KiOR-CPFD team reduced the hydrodynamics validation problem to four key milestones. Each milestone needs independent experimental validation, and must build on the previous ones: …

Applications Of Tribology And Fracture Mechanics To Determine Wear And Impact Attrition Of Particulate Solids In Cfb Systems, Ronald W. Breault, Samuel C. Bayham, Esmail R. Monazam

Fluidization XV

In recent years, much attention has been focused on the development of novel technologies for carbon capture and chemicals production that utilize a circulating fluidized bed configuration; examples include chemical looping combustion and circulation of temperature swing adsorbents in a CFB configuration for CO2 capture. A major uncertainty in determining the economic feasibility of these technologies is the required solids makeup rate, which, among other factors, is due to impact and wear attrition at various locations, including standpipes, cyclones, and the gas jets in fluid beds. While correlations have been developed that estimate the attrition rates at these areas, these …

Combustion Of Lignin-Rich Residues With Coal In A Pilot-Scale Bubbling Fluidized Bed Reactor, Roberto Solimene, Riccardo Chirone, Antonio Cammarota, Nicola Rossi, Paolo Leoni, Piero Salatino

Fluidization XV

The deployment and the exploitation of bioethanol as automotive fuel became more and more relevant to reduce the emissions of greenhouse gases and to limit the dependence on countries supplying fossil fuels. However, the production of second-generation bioethanol, i.e. using lignocellulosic biomass or scraps of agricultural crops as feedstock, generates a waste stream consisting of lignin-rich residues whose fate has to be found (1-2). This work aims at investigating the combustion of lignin-rich residues (in the following simply called lignin), coming from a second-generation bioethanol production plant, with coal in a pilot-scale bubbling fluidized bed combustor (FBC). The pilot-scale 200kW …

Experimental Study Of Solid Mixing Mechanism In A 2d Fluidized Bed, J. Sánchez-Prieto, A. Soria-Verdugo, L.M. García-Gutiérrez, F. Hernández-Jiménez, F. Suárez-Gómez

Fluidization XV

The main mechanism of solids mixing in bubbling fluidized beds is well understood. When a bubble rises through the bed, it carries a wake of particles to the bed surface. A downflow of solids exists in the region surrounding the rising bubbles, resulting on an overall convective circulation of particles in the axial direction (1).

In this work, a new method to characterize solids mixing in a 2D fluidized bed is developed. This mixing index is able to macroscopically characterize the rate of mixing in a fluidized bed by means of DIA. The mixing index is analogous to the Lacey’s …

Microscopic Modelling Of Capillary Liquid Bridge Force And Volume Repartition For Dem Simulations Of Polydisperse Systems, Alberto Di Renzo, Andrea Lorenti, Francesco P. Di Maio

Fluidization XV

Many fluidization processes like granulation, agglomeration, encapsulation or coating exhibit conditions where liquid bridges form between particles (1), resulting in strong particle-particle interactions at the microscopic scale. DEM and DEM-CFD simulations are able to show how the particle-scale phenomena determine the overall behavior of a wet particulate material in industrial systems.

Description of the capillary interaction between spherical particles in the pendular regime (i.e. with liquid bridges forming on a one-to-one basis) has been long studied and characterized, particularly in the case of spheres of the same size. When polydisperse systems are considered, the formation, interaction force and rupture of …

Recirculating Fluidized Bed Reactor For Chemical-Looping, Raman Sharma, Mines Paristech, Arnaud Delebarre, Babu Alappat

Fluidization XV

Chemical-Looping Combustion (CLC) is an oxy-combustion CO₂ capture technique. CLC involves metal oxides to split the combustion in oxidation and reduction cycles. A wide variety of reactors, single as well as interconnected, have been tested for CLC. These reactor configurations have some operational and process difficulties associated with them. A single Recirculating Fluidized Beds (RCFB) reactor configuration is proposed here for CLC with a feeling that it can overcome some of these problems. RCFB is a spouted fluidized bed with a central riser tube and the outer tube is known as downcomer. A cold model of RCFB reactor was …

Comparison Of Optical Probes And X-Ray Tomography For Bubble Characterization In Fluidized Bed Methanation Reactors, F. Schillinger, S. Maurer, T.J. Schildhauer, S.M.A. Biollaz, E. C. Wagner, R.F. Mudde, J.R. Van Ommen

Fluidization XV

The performance of many fluidized bed reactors strongly depends on the bubble behavior since they influence the mass transfer to the dense phase where the catalyst is present. An example is the methanation in a fluidized bed that allows for conversion of unsaturated hydrocarbons in the gasification gas without catalyst deactivation [1]. The BFB reactor is a very challenging step in the process chain to produce SNG out of biomass as feedstock since next to the bubble behavior a lot of other parameters like temperature, pressure, particle size, attrition of the catalyst, internals, bed height and reactor diameter etc. affect …

Attrition Of Methanol To Olefins Catalyst In A Jet Cup, Mao Ye, Zhongmin Liu, Yinfeng Zhao, Jingai Haoa

Fluidization XV

No abstract provided.

Simulation Of Fuel Particles Motion In A 2d Fluidized Bed Using A Hybrid-Model Considering Wall Friction, L.M. Garcia-Gutierrez, F. Hernández-Jiménez, A. Soria-Verdugo, A. Acosta-Iborra

Fluidization XV

The mixing of fuel particles is a key issue on the performance of fluidized bed reactors. In this work, the motion of a non-reactive fuel particle in a 2D bubbling fluidized bed at ambient conditions is simulated employing a hybrid-model. The hybrid-model, implemented in the code MFIX, simulates the dense and gas phases using a Two-Fluid Model (TFM) while the fuel particles are modeled using a Discrete Element Method (DEM). The importance of the present hybrid-model is that the interaction of the continuum phases with the fuel particles behavior is fully coupled.

In a previous study, Hernández-Jiménez et al. (1) …

Micro/Meso Simulations Of A Fluidized Bed With Heat Transfer, Florian Euzenat, Anthony Wachs, Abdelkader Hammouti, Pascal Fede, Eric Climent

Fluidization XV

Particulate flows encountered in fluidized beds are frequently used in industrial applications (refining, energy, chemicals/petrochemicals, pharmaceutics). The wide range of spatial scales and interactions between the phases in such systems yields a complex flow often coupled with mass and/or heat transfer. These transfer have been widely investigated in the past in an experimental and numerical manners for dilute (1, 2) and dense suspensions (3, 4).

Multi-scale modeling is a numerical approach developed to understand these phenomena from the particle scale (microscale) to process unit (macroscale). An intermediate scale (mesoscale) ranging from 10⁴ to 10⁸ particles is also introduced. …

Cold Flow Modelling Of Char Concentration In The Recirculated Bed Material Stream Of A Dual Fluidized Bed Steam Gasification System, Stephan Kraft, Friedrich Kirnbauer, Hermann Hofbauer

Fluidization XV

The dual fluidized bed (DFB) steam gasification technology of biomass was developed at Vienna University of Technology and is well-established for transforming biomass into a product gas which can be used for further applications. The DFB steam gasification reactor consists of a gasification chamber (bubbling bed, fluidized with steam) and a combustion chamber (turbulent bed, fluidized with air). Biomass is fed into the gasification chamber and gets in contact with the bed material, typically Olivine, at about 840°C. The released volatiles leave the gasification reactor as product gas. A part of the solid residue, called char, flows with the bed …

Cold Flow Modelling Of Dual Fluidised Bed Pyrolysis, Christoph Pfeifer, Gregor Tondl, Andreas Frohner

Fluidization XV

High temperature pyrolysis at about 600-700°C of carbon containing waste materials (plastic waste, shredded old tires, biogenic residues, etc.) is an attractive technology for substitution of fossil fuels in industrial processes. A dual fluidized bed system is investigated in a scaled cold flow model. This model consists of a riser as combustion section and a bubbling fluidized bed as pyrolysis section. The pyrolysis section is aimed to convert the solid feed material into pyrolysis oil as well as permanent gas components. This gas stream can be directly used e.g. in rotary kilns at temperatures of 400-600°C with high tar content …

Hydrodynamic Study Of A Circulating Fluidized Bed Used For Biomass Gasification Between 20 °C And 900 °C, Sébastien Pecate, Mehrdji Hemati, Mathieu Morin, Yilmaz Kara, Sylvie Valin

Fluidization XV

This work, carried out in the GAYA project frame and subsidized by ADEME, concerns the hydrodynamic study of a 60 kWth circulating fluidized bed pilot plant constructed at the Laboratoire de Génie Chimique in Toulouse for biomass gasification. In that process, biomass gasification and heating of fluidisation material (sand, olivine, catalyst…) which also acts as heat transfer medium, are performed in two separate reactors: a dense fluidized bed and a transported bed. Thermal energy, required in order to heat the fluidisation material, is supplied by the partial combustion of the char produced in the gasification reactor. The hydrodynamic study carried …

Cfdem® Modelling Of Particle Coating In A Three-Dimensional Prismatic Spouted Bed, Swantje Pietsch, Stefan Heinrich, Frank Kleine-Jäger, Michael Schönherr, Katja Karpinski

Fluidization XV

Particles which are difficult to handle in fluidized beds, such as big and non-spherical or small and co-/adhesive ones, can be fluidized in spouted beds. Nowadays, spouted bed processes are used for e.g. drying, spray granulation, encapsulation, and coating. Enhanced heat and mass transfer and intensive particle circulation allow a homogeneous distribution of the coating suspension on the particles accompanied by reduced agglomeration tendency. In the considered prismatic spouted bed the fluidization gas enters the bed chamber through two adjustable inlet slots. The coating suspension is sprayed via a two-fluid-nozzle in bottom-spray configuration (figure 1).

The simulation of the spouted …

High Solar Flux Heating Of Upflow Bubbling Fluidized Bed Circulating In Opaque Vertical Tube - 3d Numerical Simulation, Hadrien Benoit, Gilles Flamant, Daniel Gauthier, Renaud Ansart, Olivier Simonin

Fluidization XV

Current solar Heat Transfer Fluids (HTF) have a limited working temperature (< 600 °C) and present operational risks. We proposed to use air-fluidized Dense Particle Suspensions (DPS), also called Upflow Bubbling Fluidized Bed (UBFB), in tubes as a new HTF and storage medium in the frame of the so-called CSP2 FP7 European project (http://www.csp2-project.eu/). UBFB can operate up to the solid sintering temperature, thus improving the plant efficiency, it has no lower temperature limitation and is riskless. The DPS capacity to extract heat from a tube absorber exposed to concentrated solar radiation was demonstrated on a single-tube experimental receiver that was tested at the focus of the CNRS 1 MW solar furnace in Odeillo. The DPS flowed upward through the absorber tube (i.d. 3.6 cm) that passed through a 50 cm high cavity where it was exposed to concentrated solar flux that heated the DPS. The tube wall-to-DPS Heat Transfer Coefficient (HTC) first values were calculated by Flamant et al. (1). A stable outlet temperature of 750 °C was reached with a metallic tube and a particle reflux in the near tube wall region was evidenced by Benoit et al. (2).

In this paper, the UBFB behavior is studied using the multiphase flow code NEPTUNE_CFD (3). Hydrodynamics of SiC Geldart A-type particles (40 µm Sauter diameter) and heat transfer imposed by a thermal flux at the wall are coupled in 3D numerical simulations. The convective/diffusive heat transfer between the gas and dispersed phase, and the inter-particle radiative transfer (Rosseland approximation) are accounted for. The numerical and experimental results are compared in order to validate the model. The heat exchange between the particles close to the tube wall and those …

Clc, A Promising Concept With Challenging Development Issues, Thierry Gauthier, M. Yazdanpanah, A. Forret, B. Amblard, A. Lambert, S. Bertholin

Fluidization XV

Chemical Looping Combustion (CLC) is a promising technique to achieve fuel combustion in a nitrogen free atmosphere, therefore giving the possibility to separate and store or use CO2. Several potential applications are considered in the field of power generation with gas, liquid and solid fuels. In the Carbon Capture, Storage and Utilization (CCSU) context, energy penalty is reduced compared to other routes. In addition, other applications of Chemical Looping are considered in the field of H2 production or gasification for instance.

In the past years, a huge effort has been conducted worldwide to investigate CLC materials and process issues. In …

Modelling Of A Chemical Looping Combustion System Equipped With A Two- Stage Fuel Reactor, Roberto Solimene, Antonio Coppola, Piero Bareschino, Piero Salatino

Fluidization XV

The proper selection of the oxygen carrier and the correct design of the fuel reactor represent the main criticalities for the success of the chemical looping combustion (CLC) process for solid fuels. In a previous work (1) a two-stage fuel reactor (t-FR), consisting of two bubbling beds in series (bottom bed and top bed) (Fig. 1), has been proposed in order to overcome the limitations of a single-stage fuel reactor (poor char conversion, slip of unburnt volatiles, extensive elutriation of char fines). A mathematical model has been developed with the aim of assessing the performances of the two-stage fuel reactor …

Determination Of Solids Circulation Rate Through Magnetic Tracer Tests, Diana Carolina Guío-Pérez, Jorge Nicolay Ferreira Cala, Tobias Pröll, Florian Dietrich

Fluidization XV

The present work proposes the determination of solids circulation rate in a freely circulating fluidized bed cold model by using a method that performs quantitative detection of fluid-dynamically similar ferromagnetic tracer particles (1). The method has already been proven for determination of particles residence time distribution with encouraging results (2). The method is based on inductance changes of a coil by effect of changes in the concentration of ferromagnetic particles in its core (Fig. 1). There is a direct correspondence between measured inductance and proportion of ferromagnetic material in the coil’s core. The tracer particles are fluid-dynamically consistent, the injection …

The Role Of Fuel Mixing On Char Conversion In A Dual Fluidized Bed Gasifier, Louise Lundberg, Antonio Soria-Verdugo, Robert Johansson, David Pallarès

Fluidization XV

Operational conditions, such as the fluidization velocity or the solids cross-flow, have been found to affect both lateral and axial mixing of fuel particles in a fluidized bed (1, 2). The fuel axial mixing has been shown to influence the heat and mass transfer between the bed and the fuel particles, which in turn affect the char conversion rate (3). Furthermore, the fuel lateral mixing affects the residence time of the fuel inside the fluidized bed reactor. The aim of this work is to investigate the effect of the operational conditions on the resulting char conversion in the gasification chamber …

Modeling And Process Features Of Plug Flow Reactor With Internal Recirculation For Biomass Pyrolysis, Kamal Adham

Fluidization XV

A new fluidized bed design is applied to the pyrolysis of biomass, in a plug-flow with internal-recirculation (PFIR) arrangement, where the movement of solids from feed zone to product zone and the circulation within a closed loop are achieved, by the use of directional high-speed tuyeres that induce both the suspension and horizontal movement of the charge. Separation between feed and product zones is provided through one or more underflow weirs. Wet and hard-to-fluidize biomass is targeted, where fluidization and pyrolysis of the feed is achieved by the internal hot sand recirculation. Plug flow allows for both stages (pyrolysis and …

High-Efficiency Mixing Of Fine Powders Via Sound Assisted Fluidized Bed For Metal Foam Production By An Innovative Cold Gas Dynamic Spray Deposition Method, Ammendola P, Raganati F, Scherillo F, Squillace A, Chirone R, Carrino L, Astarita A, Viscusi A

Fluidization XV

Metal foams are an interesting class of materials with very low specific weight and unusual physical, mechanical and acoustic properties due to the porous structure (1). These materials are currently manufactured by means of several conventional processes (2), limited by the impossibility to produce foams with complex geometry. This paper deals with the study of an innovative method to produce complex shaped precursors for aluminum foams through cold gas dynamic spray deposition process (CGDS), aluminum alloy (AlSi12) and titanium-hydride (TiH2) being the metal and the blowing agent, respectively. However, the success of this approach strongly depends on the achievement of …

Experimental And Simulation Study On Heat Transfer In Fluidized Beds With Heat Production: An Integrated Dia/Piv/Ir Technique And Cfd-Dem, Zizi Li, Tom C.E. Janssen, Martin Van Sint Annaland, J.A.M. Kuipers, Niels G. Deen

Fluidization XV

As a result of highly exothermic reactions taking place in gas-phase olefin polymerization fluidized bed reactors, difficulties concerning the heat management play an important role in the optimization of these reactors. To get a better understanding of the particle temperature distribution in fluidized beds, a high speed infrared (IR) camera and a visual camera have been coupled to obtain the hydrodynamics and thermal aspects of a pseudo-2D fluidized bed (1), as shown in figure 1. The hydrodynamics are characterized by digital image analysis and particle image velocimetry (DIA/PIV) and the heat properties by IR. The experimental data is used to …

Catalytic Ash Free Coal Gasification In A Fluidized Bed Thermogravimetric Analyzer, Said Samih, Jamal Chaouki

Fluidization XV

Catalytic ash free coal gasification was investigated in the newly developed fluidized bed thermogravimetric analyzer. The total yield obtained from the fluidized bed TGA showed good agreement with the total gas product. For char gasification, the values of activation energy and pre-exponential factor were similar to those obtained from coal gasification in our previous work. The activation energy for the CO shift reaction decreased by 56% and 37% from the value reported in our previous work for coal gasification and in literature for catalytic coal gasification respectively. For the methane reforming reaction, the value of the activation energy was reduced …

Fundamentals Of Rotating Fluidized Beds And Application To Particle Separation, Justin M. Weber, Richard C. Stehle, Ronald W. Breault, Larry Shadle

Fluidization XV

Rotating fluidized beds provide unique opportunities to exploit fluidization under higher particle forces. The centripetal force in a rotating bed is typically on the order of 10 times the force of gravity. Since the force keeping the particles in the unit is larger, the drag force can also be larger, allowing for higher gas velocities. This operating regime provides opportunities for higher mass transfer, heat transfer, gas throughput, and bubble suppression.

One application for using a rotating fluidized bed in in Chemical Looping Combustion (CLC). When solid fuels are used, oxygen carrier and ash are mixed in the process. In …