Chemical Engineering Commons^™

New Hybrid Cpu-Gpu Solver For Cfd-Dem Simulation Of Fluidized Bed, Reza Zarghami, N. Mostoufi, H. R. Norouzi

Fluidization XV

Modeling is an alternative to experiment to explore more in multiphase flows. Various modeling approaches have been developed and used from 1D models in the macro-scale to multidimensional models in the micro scale. Well-known modeling approaches for fluidization systems are TFM and CFD-DEM, both have found many practical applications in fluidization systems. The TFM considers both fluid and particulate phase as interpenetrating continua. In contrast, the CFD-DEM considers the fluid as a continuous fluid in the meso-scale (cell-scale) and the solid as discrete particles in the micro-scale. The translational and rotational motions of individual particles are described by applying Newton’s …

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 …

Mixing And Segregation In Fluidized Bed Thermochemical Conversion Of Biomass, Piero Salatino

Fluidization XV

The recent shift in policy intentions catalysed by COP21 is stimulating the much-needed global energy transition giving new momentum to the move towards a lower-carbon and more efficient energy system. Bio-based energy and chemicals are taking the lead in the progress toward extensive replacement of fossil resources with renewables.

Fluidized bed thermochemical conversion of biomass (combustion, gasification, pyrolysis) displays a long record of successes, spanning from lab- to industrial scales, and stems out as the most viable pathway for the exploitation of biogenic fuels, either alone or in combination with fossil fuels. In spite of its diffusion, there are still …

Cfd-Dem Modeling Of Fluidized Beds With Heat Production: Influence Of The Particle Size Distribution And Heat Source, Zizi Li, Martin Van Sint Annaland, Niels G. Deen, J.A.M. Kuipers

Fluidization XV

Gas-phase polyolefin polymerization processes are executed in fluidized beds. The particles often have a broad particle size distribution (PSD) due to a variety of factors (e.g. residence time distribution, initial catalyst size distribution, different rate of catalyst activity decay, etc.). The heat transfer phenomena of particles in poly-disperse beds with different particle size distributions have been numerically analyzed using an in-house developed 3-D computational fluid dynamics and discrete element model (CFD-DEM) (1). Simulations have been carried out for beds with Gaussian PSD’s using three different distribution widths, viz. a narrow, medium and broad distribution (see figure 1), but with the …

Fluid-Dynamic Study On A Multi-Stage Fluidized Bed Column For Continuous Co2 Capture Via Temperature Swing Adsorption, Schöny. G, Zehetner. E, Fuchs. J, Hofbauer. H, Pröll. T

Fluidization XV

Adsorption based processes have a great potential to significantly reduce the overall costs of CO2 separation from stack flue gas as compared to currently available technologies. One of the main challenges in the development of these processes is certainly the provision of adequate adsorbents. Hence, in the last decade a great effort has been put into screening and testing of various adsorbent materials.

However, beside the identification of suitable adsorbent materials it is of equal importance to develop suitable reactor designs that allow for effective and most cost efficient utilization of these materials and so far only little work has …

Dynamic Flowsheet Simulation Of Gas And Solids Flows In A System Of Coupled Fluidized Bed Reactors For Chemical Looping Combustion, Johannes Haus, Ernst-Ulrich Hartge, Stefan Heinrich, Joachim Werther

Fluidization XV

A novel flowsheet simulation environment is applied to the Chemical Looping Combustion of solid fuels in order to capture dynamic behavior of fluid dynamics inside the system. The process itself is carried out in the majority of cases in a pair of strongly coupled fluidized bed reactors. The plant operated at the TUHH, which is simulated there, comprises a circulating fluidized bed air reactor and a two-stage bubbling bed fuel reactor demonstrated in the Figure.

The modelled riser of the circulating fluidized bed system consists of a dense bottom phase and a dilute upper part. The fuel reactors are implemented …

Monitoring Of The Hydrodynamic Instabilities In Conical Spouted Beds By Recurrence Plot Analysis Of Pressure Fluctuations And Acoustic Emission Signals, Rahmat Sotudeh-Gharebagh, Chiya Savari, Navid Mostoufi, Reza Zarghami, Gorkem Kulah, Murat Koksal

Fluidization XV

Spouted beds are extensively used in coating and granulation processes with the presence of liquid in the bed (1). The liquid may increase particle cohesiveness and result in de-spouting, leading to the bed malfunctioning. Hydrodynamic of the bed may alter over time due to instabilities imposed by particle size changes and cohesiveness. Therefore, conditional monitoring of spouted beds is crucial since the performance of these beds strongly depends on its hydrodynamics. A method capable of detecting bed instabilities may not be only useful for preventing undesirable situations (e.g., agglomeration and de-spouting), but also may be utilized to control the product …

Numerical Simulation Of Hydrogen Production By Chemical Looping Reforming In A Dual Interconnected Fluidized Bed Reactor, Piero Bareschino, Roberto Solimene, Giuseppe Diglio, Erasmo Mancusi, Francesco Pepe, Piero Salatino

Fluidization XV

Although exploitation of dual interconnected fluidized bed systems (DIFB) is currently being explored in various fields (1,2), DIFBs present some criticalities, mainly related to effective control of solids recirculation and to avoidance of gas leakage between the beds, extremely critical in chemical looping reforming (CLR) for hydrogen production. For the latter, the choice of the degree of oxygen carrier oxidation/reduction, operation temperature and loop design makes the design even more challenging. This paper aims at quantitative assessment of the influence of design variables by means of the numerical simulation of a DIFB-CLR process operated at steady state. The model couples …

Influence Of Bubble Bursting On Heat Transfer Phenomena In Directly Irradiated Fluidized Beds, Roberto Solimene, Claudio Tregamb, Piero Salatino, Riccardo Chirone, Fabio Montagnaro

Fluidization XV

Concentrating Solar Power (CSP) is a fast-growing technology in which several hundreds/thousands of optical mirrors concentrate the solar energy onto a receiver. The received energy can be used to produce electricity through thermodynamic cycles or to drive an endothermic chemical reaction for chemicals production (e.g. solar fuels) or for chemical storage. The receiver is a crucial part of the whole system, as it owns the severe task of collecting and transferring the concentrated solar energy minimizing the heat losses. Dense fluidized beds have been proposed as CSP receivers thanks to their large heat-transfer and thermal diffusivity coefficients, and their use …

Measurement Of Penetration And Cycle Time Of Jets From An Industrial Fluid Coking Spray Nozzle, Francisco Sanchez Careaga, Cedric Briens, Franco Berruti

Fluidization XV

Fluid Coking^TM is a process to upgrade heavy oils through thermal cracking. Oil is injected in a downward-flowing bed of hot coke particles, where it heats up and cracks into smaller vapour molecules. The down-flowing coke particles are sent to a burner where they are reheated and send back to the reactor to provide heat for cracking reactions. Liquid sprayed with atomization gas into a fluidized bed forms a jet cavity that absorbs bubbles from the bubbling bed and periodically releases a large bubble from its tip. The jet penetration length, thus, cycles. With a faster jet cycle, the …

Using Of Spouted Bed Spray Granulation Process For Fabricating Of Metal/Ceramic-Polymer Composites, Eduard Eichner, V. Salikov, M. Dosta, S. Heinrich, G.A. Schneider

Fluidization XV

Naturally occurring structural materials are composites with very high filling degrees on hard constituent. In recent years structure and properties of biological materials have been studied in detail. But it has not been possible to reconstruct this structural design. In this contribution we present a process for the fabrication of very highly filled composite materials by using of the spouted bed spray granulation process.

Spouted bed granulation offers many advantages for the design of composite materials. In this investigation fine particles (dP =10-50 µm) could be uniformly spouted, and optimal properties for further processing to bulk materials can …

Catalyst Preparation For Fluidized Bed Reactors By Spray Drying, Nooshin Saadatkhah, Gregory S. Patience, Daria C. Boffito, Marco G. Rigamonti, Seyedfoad Aghamiri, Mohammad Reza Talaie

Fluidization XV

Spray dried fluidized bed catalysts belong to the Geldart Group A classification and vary between 22 m to 200 m in diameter (1). Binder is either distributed throughout the particle with the active phase or surrounds the active phase as in a core-shell structure (2, 3). We slurried WO₃/TiO₂ micronized powder (0.2 m to 2 m) with colloidal silica (LUDOX^® HS-40) to form a slurry with a mass fraction of 5 % to 20 % solids. The solution entered the top of GB-22 Yamato fluidized bed spray dryer chamber (0.12 m ID) through a two-fluid nozzle …

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 …

A Multi-Stage Fluidized Bed System For Continuous Co2 Capture By Means Of Temperature Swing Adsorption – First Results From Bench Scale Experiments, Schöny G, Florian Dietrich, Fuchs. J, Hofbauer. H, Pröll. T

Fluidization XV

Temperature swing adsorption processes have been proposed as an alternative to common amine scrubbing processes for CO2 capture from stack flue-gas streams, as they have the potential to reduce the overall capture costs significantly. In the recent years, researchers have put a great effort into the development of highly selective CO2 adsorbent materials with sufficiently large CO2 transport capacities and cyclic operating stability. However, comparably little work has been attributed to the development of suitable reactor designs or to the experimental study of continuously operated temperature swing adsorption (TSA) processes that utilizes those adsorbent materials.

The authors of this work …

Dense Gas-Particle Suspension Upward Flow Used As Heat Transfer Fluid In Solar Receiver: Pept Experiments And 3d Numerical Simulations, Renaud Ansart, Pablo Garcia-Triñanes, Benjamin Boissière, Hadrien Benoit, Jonathan Seville, Olivier Simonin

Fluidization XV

Dense particle suspension, also called an Upflow Bubbling Fluidized Bed (UBFB), is an innovative alternative to the heat transfer fluids classically used in concentrated solar power (CSP) plants. Indeed, such fluids have several limitations: restricted range of operating temperatures, significant safety issues, corrosion problems and high maintenance costs. The CSP2 (Concentrated Solar Power in Particles) FP7 European project (http://www.csp2-project.eu/) has the ultimate goal of developing commercially-viable CSP plants based on granular media as the heat transfer fluid, where power is transmitted to the particles by the receiver walls (metal or ceramic), which are themselves subject to solar radiation. An additional …

Validation Of The Oxygen Buffering Ability Of Bed Materials Used For Ocac In A Large Scale Cfb Boiler, Angelica Corcoran, Fredrik Lind, Henrik Thunman

Fluidization XV

Fluidized bed combustion is widely considered an advantageous technology managing moist and heterogeneous fuels due to the heat storage in the bed material and its favorable conditions regarding fuel and oxygen mixing throughout the combustion chamber. Even though mixing is often regarded as sufficient, the technology remains sensitive to variations in load and heterogeneity of fuels, leading to an uneven distribution of oxygen in time and space of the furnace. The remedy has nearby exclusively been related to the supply of air, particularly considering a surplus of air and positioning of injection ports.

An applicable combustion concept, oxygen carrier aided …

A 1.5d Model Of A Complex Geometry Laboratory Scale Fuidized Bed Clc Equipment, Jaroslaw Krzywanski, A. Żylka, T. Czakiert, K. Kulicki, S. Jankowska, W. Nowak

Fluidization XV

The awareness of the climate changes has resulted in the development of new technologies allowing to increase the effectiveness and to lower the costs of CO2 separation from the flue gas. One of the most promised combustion technology of fossil fuels is Chemical Looping Combustion (CLC). The technology is considered to be one of the cheapest techniques for CO2 capture (1). Since it is still an emerging technology and the complexity of processes are still not sufficiently recognized, the development of a simple model of CLC equipment is of practical significance.

The paper presents a 1.5D model of the laboratory-scale …

Effect Of Interactions Between Spray Jets On Liquid Distribution In A Fluidized Bed, Helal Elkolaly, Cedric Briens, Franco Berruti

Fluidization XV

In Fluid CokersTM, banks of spray nozzles are used to inject oil in a bed of hot coke particles. The purpose of this study is to determine whether interactions between spray jets could enhance liquid distribution on hot coke particles, which is crucial to improve the operability and performance of Fluid Cokers.

A low temperature experimental model of Fluid Coking was used to measure the liquid distribution. Preliminary screening of nozzle positions employed conductance measurements. A binder solution was utilized to further investigate the most interesting nozzle interactions, by simulating at low temperature the formation of agglomerates during high temperature …

Experimental Characterization Of Operational Regimes In Low Aspect-Ratio Cfb Risers, Tove Karlsson, Xuemin Liu, Filip Johnsson, David Pallarès

Fluidization XV

This work discusses operational regimes in CFB-furnaces by means of mapping the relation between fluidization velocity, riser pressure drop and external solids circulation. A cold CFB unit with riser dimensions 0.8 × 0.12 × 8.5 m is used, thus yielding a riser height-to-width aspect ratio of 10.6, similar to that of typical CFB boilers (1). The overall flow regime established in the unit has been shown to be representative for large-scale CFB boilers, while providing the opportunity to investigate a wide range of operational parameters, including such that are not easily applicable to real boilers. The operational conditions covered fluidization …

Effect Of Steam On The Performance Of Ca-Based Sorbents In Calcium Looping Processes, Fabio Montagnaro, Eduardo Gais, Antonio Coppola, Piero Salatino, Fabrizio Scala

Fluidization XV

Calcium looping, a post-combustion “carbon capture and storage” process (see Figure 1), is usually carried out by means of a limestone-based sorbent in a dual interconnected fluidized bed reactor. The two stages of this process are limestone calcination and carbonation: in the former case, water vapor can be present as a product of the auxiliary fuel combustion needed to drive this endothermal step; in the latter case, water vapor is usually present in the combustion flue gas stream bearing the CO2 to be captured. This work pursues previous research concerning the hydration-induced reactivation of spent sorbents (1,2,3) further and aims …

The Relationship Between Fluidized Bed Electrostatics And Entrainment, John R. Grace, Turki Alsmari, Xiaotao Bi, Farzam Fotovat

Fluidization XV

Existing methods of predicting entrainment from gas-fluidized beds, based exclusively on hydrodynamic variables and mechanisms, show extremely wide discrepancies in their predictions and often deviate by many orders of magnitude from experimental values. Based on simultaneous measurement of electrostatic charges in the freeboard region and entrainment, this paper will show that inter-particle electrostatic forces on relatively fine particles can be at least of the same order of magnitude as the gravity forces that must be overcome for entrainment to take place. Moreover, incorporation of a term for inter-particle electrostatic force leads to substantial improvement in the ability to correlate our …

Influence Of Catalyst Conditioning On Products In A Continuously Operated Fcc Pilot Plant, Matthias Swoboda, Josef Fimberger, Alexander Reichhold

Fluidization XV

In the past, the industrially proven and well established process of FCC has been used primarily to increase the product yield of the gasoline fraction in the refinery process. Economic and political considerations caused a shift of interest to other FCC-products (light olefins and LCO for example (1)) and the use of alternative feedstocks like vegetable oils (2). Another way to obtain the varying desired results is the development of new FCC catalysts.

In this study, one such, as of yet non-commercial catalyst was used. The focus lay on the relation between catalyst activity and related composition of the products …

First Experience In Operation Of Cold Model Of Fb-Clc-Sf (Fluidized-Bed Chemical-Looping-Combustion Solid-Fuels) Facility, Tomasz Czakiert, Krzysztof Kulicki, Jaroslaw Krzywanski, Anna Zylka, Sylwia Jankowska, Wojciech Nowak

Fluidization XV

The first experiences with the cold model of dual fluidized bed unit designed for chemical looping combustion of solid fuels (FB-CLC-SF) will be presented.

The constructed facility combines two different type reactors. The first one, which is the Air Reactor (AR) is operated in a regime of fast fluidized bed, whereas, the second one, which is the Fuel Reactor (FR) works under bubbling fluidized bed conditions. However, the integrated reactors make the whole construction being a CFB-type (Circulating Fluidized Bed) unit. The facility is made entirely of transparent material (Plexiglas). This feature supports effectively the measurements, which enables to conduct …

Effect Of Bed Particle Size On Heat Transfer Between Fluidized Bed Of Group B Particles And Vertical Rifled Tubes, Artur Blaszczuk, Wojciech Nowak, Jaroslaw Krzywanski

Fluidization XV

The effect of bed particle size on the local heat transfer coefficient between a fluidized bed and vertical rifled tubes (38mm-O.D.) has been determined in a large-scale circulating fluidized bed (CFB) reactor. Bed particles with different Sauter mean particle diameter within the range of 0.219-0.411mm and particle density in the range of 2660-2750 kg/m3 were used as bed material in this heat transfer study. A gas fluidized bed furnace with 27.6´10.6m cross-section above refractory line and 48m in height was used. Air coal firing conditions at the membrane wall in the form of water tubes welded with lateral fins corresponded …

Three-Dimensional Cfd Simulation Of The Regeneration Of Mgo-Based Sorbent In A Carbon Capture Process, Hamid Arastoopour

Fluidization XV

Carbon dioxide is the primary greenhouse gas emitted through human activities; therefore, efficient reduction of CO2 is regarded as one of the key environmental challenges of the current century. Different processes have been introduced in the literature for CO2 capture; among these solid sorbent processes have shown potential advantages. In order to achieve steady CO2 capture using solid sorbents, a circulating fluidized bed (CFB) is used that consists mainly of a carbonator reactor (where the CO2 is adsorbed by solid sorbents) and a regenerator (where carbonated sorbents release CO2 and a concentrated CO2-steam mixture is produced). Different solid sorbents have …

Analysis Of Fluctuations In Velocities, Voidage And Gas Concentration In Cfb Conditions, Timo Niemi, Sirpa Kallio, Juho Peltola

Fluidization XV

The purpose of the present study is to evaluate the possibilities to estimate the fluctuation characteristics of gas concentrations in a CFB from the characteristics of velocity and voidage fluctuations. In CFB combustion, the local concentrations of reactant gases strongly fluctuate which affects the reaction rates. In CFD modeling, the effect of turbulent mixing on reaction rates is commonly taken into account by means of mixing descriptions based on fluctuation time scales. For fast reactions the mixing rate can be the rate limiting step. Similar to gas phase reactions, for heterogeneous combustion of solid fuel, fluctuations in gas concentrations should …

Solid Flux In Travelling Fluidized Bed Operating In Square-Nosed Slugging Regime, Sina Tebianian, Kristian Dubrawski, Naoko Ellisa, John R. Grace, Thomas W. Leadbeater, David J. Parker, Rouzbeh Jafari, Jamal Chaouki, Pablo Garcia-Trinanes, Jonathan P. K. Seville

Fluidization XV

The performance of gas-fluidized bed reactors depends significantly on their hydrodynamics. Among the important properties that dictate the characteristics of a gas-fluidized bed, local solid flux plays a significant role, influencing vital parameters such as bed-to-surface heat exchange and solid circulation rate. Developing techniques that can provide accurate measurements of solid flux is extremely important for: 1) assessing the accuracy of other measurement techniques applicable to industrial units, and 2) validation of CFD models.

Comparison of different measurement techniques that provide similar hydrodynamic information is helpful in assessing the errors associated with each methodology. Most measurement techniques for obtaining solid …

Impact Of Local Fluidized Bed Hydrodynamics On Interactions Between Particles And Gas-Liquid Sprays, Maryam Mohagheghi, Franco Berruti, Cedric Briens

Fluidization XV

In the Fluid CokingTM process, heavy oil is sprayed into a downward-flowing fluidized bed of hot coke particles. A good liquid distribution on the particles is essential to achieve a high yield of desirable liquid products and avoid operating problems. This presentation shows how to modify local bed hydrodynamics to improve liquid distribution.

The distribution of the injected liquid in the bed can be improved by either increasing the atomization gas flowrate or, preferably, the local fluidization velocity. Study of nozzles at different locations and inclinations identifies the dominant effects of bed hydrodynamics at the nozzle and jet tips on …

The Effect Of Riser End Geometry On Gas-Solid Hydrodynamics In A Cfb Riser Operating Above Fast Fluidization Regimes, Larry Shadle

Fluidization XV

Riser hydrodynamics are a function of the gas and solids flow rates as well as the exit geometry, particularly when operated above the upper transport velocity. This work compares the exit voidage for multiple geometries and two different Geldart class B solids: glass beads and coke. Geometries were changed by modifying the volume of an abrupt T-shaped exit above the lateral riser exit. This was accomplished by positioning a plunger at various heights above the exit from zero to 0.38 m. A correlation was developed for the exit voidage as a function of the noted length and the following hydrodynamic …