Chemical Engineering Commons^™

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 …

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 …

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 …

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 …

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 …

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 …

A Twin-Bed Test Reactor For Characterization Of Calcium Looping Sorbents, Antonio Coppola, Fabrizio Scala, Piero Salatino, Liberato Gargiulo

Fluidization XV

The reduction of sorbent CO2 capture capacity and the extent of particle attrition over iterated cycles are relevant to design of Calcium Looping processes (1-2). Thermogravimetric analyzers or fluidized bed reactors are generally used to evaluate the sorbent performance. One drawback of these reactors is that they do not reproduce the thermal history that is actually experienced by sorbent particles in real looping cycles. In this study, a novel experimental technique is proposed to overcome this limitation. The apparatus consists of two interconnected fluidized bed reactors operating as calciner and carbonator, respectively (Fig. 1). The two reactors are connected each …

Development And Study Of Measurement Methods For Bogging In A Fluidized Bed, Majid Hamidi, Franco Berruti, Cedric Briens

Fluidization XV

In the Fluid CokingTM process, heavy oil is contacted with hot fluidized coke particles. If the local concentration of liquid is too high, particles may stick together, resulting in poor fluidization or even defluidization, a condition commonly known as "bogging". Earlier studies, presented at Fluidization XIV, used capacitance sensors to show how bogging affects bubble properties and the distribution of liquid sprayed into a fluidized bed. The objective of this study is to identify other, more practical methods for early bogging detection.

Methods using pressure measurements or active sound transmission are presented. A Kolmogorov-Smirnov test of the wavelet coefficients of …

Collision Dynamics Of Colliding Wet Solids: Rebound And Rotation Analysis, Britta Crügera, Stefan Heinrich, Yali Tang, Jochem Scholte, Niels G. Deen, J.A.M. Kuipers

Fluidization XV

Fluidization processes are characterized by intense particle-particle and particle-wall contacts. In coating, granulation and agglomeration processes moreover liquids are involved in the form of liquid layers or droplets on the particle surface. Therefore, the knowledge about collision dynamics of wet solids is fundamental for the exact description of such processes.

In this work collision dynamics are analyzed via coefficients of restitution. The coefficient of restitution is defined as ratio of rebound to impact velocity and as such it characterizes the energy dissipated during collision. It is an important parameter for DEM simulations and depends strongly on the collision parameters (such …

Spouted Bed Design Considerations For Coated Nuclear Fuel Particles, Douglas W. Marshall

Fluidization XV

High Temperature Gas Cooled Reactors (HTGRs) are fueled with tristructural isotropic (TRISO) coated nuclear fuel particles embedded in a carbon-graphite fuel body. TRISO coatings consist of four layers of pyrolytic carbon and silicon carbide that are deposited on uranium ceramic fuel kernels (350µm – 500µm diameters) in a concatenated series of batch depositions. Each layer has dedicated functions such that the finished fuel particle has its own integral containment to minimize and control the release of fission products into the fuel body and reactor core. The TRISO coatings are the primary containment structure in the HTGR reactor and must have …

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 …