Engineering Commons^™

Evaluation Of A Lagrangian Discrete Phase Modeling Approach For Application To Industrial Scale Bubbling Fluidized Beds, Schalk Cloete, Shahriar Amini, S.T. Johansen, M. Braun, B. Popoff

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

Industrial scale bubbling fluidized bed simulations were carried out within the Kinetic Theory of Granular Flows (KTGF). The KTGF was applied within two different modelling frameworks, the traditional Two Fluid Model (TFM) and a new approach in the form of the Dense Discrete Phase Model (DDPM), in order to identify any differences in performance. Only the DDPM was able to attain fully grid independent results for industrial scale 2D simulations. In fact, the performance was sufficiently good to enable the completion of reasonably affordable full 3D simulations. These simulations revealed some differences between 2D and 3D, but the global system …

Comparison Of Entrainment Rate In Acrylonitrile Reactors Using Plant Data And Cfd Simulations, S. Moffatt, S. Ramchandran, P. Zhao, K. Williams

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

Accurate entrainment rates are important in fluidized bed reactors for several reasons, including determination of cyclone loadings and efficiencies, sizing of diplegs, and inputs to population balance models. Entrainment correlations exist in the literature and from other sources to predict entrainment rates from fluidized beds, but they can vary by orders of magnitude. In addition, many correlations do not take into account effects of internals which are present in many types of industrial reactors. A study was undertaken to better understand entrainment rates from Sohiotype acrylonitrile fluidized bed reactors containing catalyst classified as a Geldart type A powder. As part …

Cfd Simulation Of Co2 Sorption In A Circulating Fluidized Bed Using Deactivation Kinetic Model, Emadoddin Abbasi, Hamid Arastoopour

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

The Computational Fluid Dynamics (CFD) approach was used to simulate sorption of CO2 using solid sorbents in the riser section of a circulating fluidized bed. The simulation results were compared with the experimental data of Korea Institute for Energy Research (KIER) for continuous CO2 sorption using potassium carbonate in a circulating fluidized bed system.

Critical Evaluation Of Euler-Euler And Euler-Lagrangian Modelling Strategies In A 2-D Gas Fluidized Bed, F. Hernández-Jiménez, J. R. Third, A. Acosta-Iborra, C. R, Müller

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

Two-phase granular systems are commonly encountered in industry, and fluidized beds are particularly important due to their excellent heat and mass transfer characteristics. Here, we critically evaluate the differences between two modelling strategies, Euler-Euler and Euler-Lagrangian models. Euler-Euler simulations were performed using MFIX and an in-house code was used for Euler-Lagrangian simulations. A 2D bed of width, height and transverse thickness of respectively, 0.2 m, 0.5 m and 0.01 m, served as a test case. The settled bed height was H0 = 0.2 m. Particles of density ρ = 1000 kg/m³ and diameter dp = 1.2 mm were fluidized with …

Particle-Fluid Flow Simulations Of An Fcc Regenerator, Sam Clark

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

A particle-fluid flow simulation of a commercial-scale fluidized catalytic cracking unit has been conducted. The simulation was full-scale, three-dimensional, and with complex internal geometries. The focus of the computational model was to predict wear on internal structures. The geometry of the particle feed pipe was found to cause asymmetric flow of high-speed gas which led to significant wear.

Time-Resolved X-Ray Tomography Of A Fluidized Bed Of Geldart A Particles, Robert Frank Mudde, Evert C. Wagner, J.R. Van Ommen, Q. Ricoux

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

This paper discusses the influence of fines on the size of bubbles moving through a 23 cm ID fluidized bed of Geldart A particles imaged with an X-ray Tomographic Scanner. In earlier work [1], the bubble distribution in a fluidized bed of Geldart B particles was shown. The current study using Geldart A particles is more challenging to the reconstruction algorithm, since there are more bubbles, and they are smaller in size. We study the influence of adding fines (i.e. particles <= 45 micron) to the system. When adding a mass fraction of fines of 24%, we find a decrease of the average bubble of 40% of the size for the original powder, in line with earlier results from pressure probes and optical probes [2]. We find that the entire distribution of the bubble sizes shifts to smaller values.

A Study Of Solids And Gas Mixing In A Partitioned Fluidized Bed, Young-Ju Seo, Solim Kang, Seung-Yong Lee, Young Cheol Park, Ho-Jung Ryu, Gyoung Tae Jin, Jong-Ho Moon

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

A partitioned fluidized bed gasifier has been developed for improving coal gasification performance. The basic concept is to divide a fluidized bed into two parts, a gasifier and a combustor, by a partition. Char is burnt in the combustor and generated heat is supplied to the gasifier by solid mixing. Therefore, solid mixing should be maximized whereas gas mixing between syngas and the combusted gas should be minimized. In this study, gas and solid mixing behaviors were verified in cold model acrylic beds. For monitoring solid mixing behavior, transient temperature trends in the beds were analyzed. A heat source and …

Cfd Modeling Of Fluidized Bed Reactor For The Synthesis Of Dimethyl Ether, Ranjeeth Kalluri, Nandita Akunuri, Aqil Jamal, Raghubir Gupta

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

The syngas-to-DME reaction is highly exothermic, and the catalyst temperature window is very narrow. The fluidized-bed reactor is, therefore, an ideal choice to carry out these reactions. RTI is developing a circulating fluidized bed design for DME synthesis. This paper discusses a two-phase CFD model and optimization of the solids circulation rate.

Dem Study Of Fluidized Bed Dynamics During Particle Coating In A Spouted Bed Apparatus, Sergiy Antonyuk, Stefan Heinrich, A. Ershova

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

A novel process for coating of spherical aerogel particles in a spouted bed is suggested. Using Discrete Element Method the influence of the density and restitution coefficient of experimentally coated aerogels on the fluidized bed dynamics in the developed apparatus was described.

A New Approach For Modeling Of A Fluidized Bed By Cfd-Dem, Shayan Karimipour, Navid Mostoufi, Rahmat Sotudeh-Gharebagh, H. Chizari

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

Numerical studies of 3D cylindrical fluidized bed by means of combined computational fluid dynamics (CFD) and discrete element method (DEM) were carried out. For motion of particles, Newton's second law and 3D compressible Navier-Stokes equations in generalized curvilinear coordinates in its conservative form were used. Navier-Stokes equations were solved with high order compact finite difference scheme by fully implicit flux decomposition method. Non-reflecting boundary conditions (NRBC) were used for the outflow boundary. The convergence of this method, especially at high Reynolds number, is significantly better than the SIMPLE method.

Ecvt Imaging Of 3-D Flow Structures And Solids Concentration Distributions In A Riser And A Bend Of A Gas-Solid Circulating Fluidized Bed, Fei Wang, Qussai Marashdeh, Liang Shih Fan

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

Experimental studies using electrical capacitance volume tomography (ECVT) are conducted to examine gas-solid flows in a riser and a bend of a 0.05 m (2 in) ID gas-solid circulating fluidized bed (CFB) system. The quantitative measurements using ECVT are made that illustrate a three-dimensional symmetric core-annulus structure in the riser and a non-centro-symmetric core-annulus structure in the bend. Results on the volume solids holdup distributions in the riser and in the bend at various operating conditions are also obtained.

Description Of Pressure Fluctuations In A Circulating Fluidized Bed By Statistical Analysis, Adam Luckos, Roelof Coetzer, Andre Mostert

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

In this paper we evaluate different methods for statistically analyzing the variability in pressure fluctuations measured at three locations in an 80-mm-ID, 5-m-tall CFB model operated with natural rutile particles and air at ambient conditions. The methods evaluated are the Shannon entropy, Fischer information matrix together with kernel density estimation, and an estimation of the magnitude of the pressure amplitudes. The accuracy of the different methods is estimated by the bootstrap method. We illustrate how informative statistics from these methods can be used to quantify the effect of the process variables on fluidization at different bed locations. Depending on the …

Characterization Of Fluidization And Mixing Of Binary Mixtures Containing Biomass At Low Velocities Through Analyzing Local Pressure Fluctuations, Farzam Fotovat, Jaber Shabanian, Jamal Chaouki, Jeffrey Bergthorson

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

To judge qualitatively the effect of biomass properties on its fluidizability and mixing tendency with sand particles at low fluidization velocities, local pressure gradients in the top and bottom of the bed were compared for all investigated systems. It was found that changing the mass fraction and the size of biomass impacted the onset of bubbling and the size of bubbles across the bed, which, in turn, affected the mixing/segregation of the bed content.

Dynamics Of Gas-Solids Fluidized Beds Through Pressure Fluctuations: A Brief Examination Of Methods Of Analysis, Srdjan Sasic, Marc-Oliver Coppens, Filip Johnsson, J. Ruud Van Ommen, John Van Der Schaaf, Stefan Gheorghiu

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

This paper revisits and critically examines a number of methods used for analysis of in-bed pressure signals recorded in gas-solid fluidized beds. The goal is to obtain information on the time scales of dominant phenomena present in the pressure time series of four fluidization regimes. It is demonstrated that the average cycle time represents an effective alternative to spectral analysis. In addition, we give evidence that the average cycle time yields equivalent information as some of the advanced methods of non-linear analysis (e.g. the Kolmogorov entropy). Finally, by using wavelets and wavelet packets, we show how to obtain an accurate …

Dynamic Characteristics Of Bubbling And Turbulent Fluidization Using Hurst Analysis Technique, H. Azizpour, Navid Mostoufi, Reza Zarghami, Rahmat Sotudeh-Gharebagh

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

A non-intrusive vibration monitoring technique was used to study the flow behavior in a fluidized bed. This technique has several advantages compared to other techniques, such as pressure probes and optical fiber probes which may influence the measurement because they are intrusive. Experiments were conducted in a 15 cm diameter by 2 m tall fluidized bed using 470 micron sand particles. Auto correlation functions, mutual information function and Hurst exponent analyses were used to analyze the fluidized bed hydrodynamics near the transition point from bubbling to turbulent fluidization regime. These methods were able to detect the regime transition point using …

Sulfur Uptake By Limestone-Based Sorbent Particles In Cfbc: The Influence Of Attrition/Fragmentation On Sorbent Inventory And Particle Size Distribution, Fabio Montagnaro, Piero Salatino, Fabrizio Scala, Massimo Urciuolo

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

This paper presents a population balance model aiming at the prediction of sorbent inventory and particle size distribution establishing at steady state in the bed of an air-blown CFBC fuelled with a sulphur-bearing solid fuel. The core of the model is represented by population balance equations on sorbent particles which embody terms expressing the extent/rate of sorbent attrition/fragmentation. The effect of the progress of sulphation on attrition and fragmentation is taken into account by selection of appropriate constitutive equations. Model results are presented and discussed with the aim of clarifying the influence of particle attrition/fragmentation on sorbent inventory and particle …

Putting Structure Into Fluidized Bed – From Concept To Industrial Applications, Fei Wei, Qiang Zhang, Guohua Luo, Weizhong Qian, Yao Wang

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

Structures of particles, particle agglomerates, distributors, and internals have significantly influence on hydrodynamics and transfer behaviors of the dense gas-solid fluidized bed. For nanomaterial production, the particle surface and their agglomerated structures directly influence the fluidization behaviors; while for coal to chemical process, the distributors, internals play an important role in regime transient, and hydrodynamics. Carbon nanotubes mass production, coal to chemicals process. and fuel production were employed as examples to describe the concept of putting structures into fluidized bed, and then to put these structures into industrial applications.

Study Of Standpipe And Loop Seal Behavior In A Circulating Fluidized Bed For Geldart B Particles, Heiko Dieter, Alexander Charitos, Ajay R. Bidwe, An Wei, Mariusz Zieba

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

The loop seal aeration effect on the supply side has been studied through small scale CFB experimentation. Parameters affected include inventory allocation and entrainment. The gas velocity in the standpipe is influenced by loop seal aeration and riser velocity. Variation in slugging behavior above and below solid downflow velocity of 0.025 m/s is analyzed and discussed here.

Observation Of Flow Regime Transition In A Cfb Riser Using An Ldv, Paul C. Yue, Joseph Mei, Lawrence J. Shadle

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

The solids flow in a circulating fluidized bed (CFB) riser is often described to have a core-annular structure. For a given superficial gas velocity, at the initial introduction of solids into a riser a flow structure of dilute upflow regime exists. Continuing to increase the solids flow in the riser transitions the flow structure to the core-annular flow regime. However, with further increase of solids flow a condition is reached, depending on the superficial gas velocity, where all the solids across the riser cross section flow upwards, even those at the wall. When the solids flux, solids fraction and gas …

Bench-Scale Investigation Of Limestone Size Evolution In A Fluidized Bed Combustor, Xuan Yao, Hairui Yang, Pierre Gauville, Hairui Yang, John H. Chiu, Shin G. Kang

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

The influence of temperature, heating rate and chemical reaction on fragmentation

and attrition of limestone in a fluidized bed (FB) was investigated. The intensity of

fragmentation and attrition was measured in the same apparatus but at different

fluidizing velocities and fluidizing media. It was found that the heating rate has a

positive effect on fragmentation for the tested limestones. The effect of bed

temperature on limestone fragmentation was inconclusive. The influence of

chemical reaction on the fragmentation seems to be complicated; CO2 release due to

calcination would prompt fragmentation while the sulfation would increase the gas

diffusion resistance and depresses …

Evolution Of Fcc - Past Present And Future And The Challenges Of Operating A High Temperature Cfb System, Ye-Mon Chen

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

The fluid catalytic cracking (FCC) process is one of the most important circulating fluidized bed processes. Although the FCC process has been in commercial operation for over 60 years, the technology continues to evolve in order to meet new challenges, which include processing more difficult feedstock and meeting more stringent environmental regulations. This paper presents selected snap-shots of a few challenges (high temperature erosion, corrosion and emission control) that the FCC process faces today and the new challenges yet to come in the near future.

Catalyst Attrition In The Cfb Riser, Andreas Thon, Marvin Kramp, Ernst-Ulrich Hartge, Stefan Heinrich, Joachim Werther

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

Catalyst attrition in the CFB riser was experimentally investigated in a pilot scale CFB system consisting of a 400 mm diameter riser with a height of 15 m, a return leg and a two-stage cyclone separation. The catalyst loss of the CFB system was measured. In order to discern between attrition occurring in the cyclones and in the riser the system was simulated by a population balance approach which takes the separation efficiency of the cyclone system into account. On the basis of the experimental investigation an empirical correlation for catalyst attrition in the CFB riser has been developed which …

The Relationship Between Fluidization Velocity And Segregation In Two-Component Fluidized Beds: A Preliminary Analysis, Brunello Formisani, Rossella Girimonte, Vincenzino Vivacqua

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

Experiments are presented that provide the initial and final fluidization velocity of binary mixtures at varying composition. Introducing just one parameter to account for their segregation level, the theoretical equations of the two characteristic velocities are derived. These equations are then employed to predict the concentration profile obtained by slowly defluidizing the bed down to the fixed state

Coal Ignition Temperature In Oxygen-Enriched Cfb Boiler, Junnan Chao, Hairui Yang, Junfu Lv, Hai Zhang, Qing Liu, Yuxin Wu

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

The oxygen-enriched Circulating fluidized bed (CFB) combustion technology is a new method to reduce CO2 emissions. The coal ignition temperature, Ti F, in an oxygen-enriched CFB boiler is an important parameter for designing the startup burner and for choosing the operating strategy during the startup process. The combustion of five types of coal under four different atmospheres (air, O2 27 %, O2 40%, O2 53%, CO2 as balance gas) was measured in a laboratory scale fluidized bed (FB) with an under-bed preheat system. Using thermocouples and a Gas Analyzer, the changes in bed temperature and the concentration of the different …

Effect Of Bed Temperature, Fuel Density And Particle Size On Hydrodynamic Parameters Of 10 Mw Fluidized Bed Combustion Power Plant Using Riser Waste, Ravi Inder Singh, S.K. Mohapatra

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

The design and operation of boilers using rice waste present a number of challenges. The overall capacity and efficiency of the boiler are strongly dependent on the fuel, and the supplier has to be able to guarantee the capacity and efficiency within the whole range of the fuel mixture being burned. It is well known that the exit gas composition is strongly dependent on the fuel. Bed temperature, fuel density and particle size significantly affect the hydrodynamic properties of a fluidized bed combustor. The effect of bed temperature, fuel density, particle size on exit gas composition and other hydrodynamic parameters …

The Variation Of The Bubble Phase Properties Of A Fcc Fluidized Bed At High Temperature, Rossella Girimonte, Brunello Formisani

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

Some important characteristics of the bubbling regime, relevant to a cut of FCC catalyst with an average size of 110 mm were investigated at 100, 400 and 700 °C. This was achieved by imploying data of bed collapse tests as well as images of the bubble eruption at the free surface of the bed by varying fluidization velocities and bed aspect ratios. The results show that a smoother regime of fluidization is observed at superambient temperature.

Effect Of Gas Bypassing In Deep Beds On Cyclone Dipleg Operation, Allan Issangya, Reddy Karri Dr, Ted Knowlton, Ray Cocco

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

Cyclone diplegs play a major role in the functioning of fluidized beds. Previous studies have shown that at certain operating conditions there can be severe gas bypassing (also referred to as jet streaming) of gas in deep beds of Geldart Group A materials which leaves significant portions of the fluid bed defluidized. If cyclone diplegs are immersed in these defluidized regions, solids discharge from the dipleg may be hindered, which can lead to the flooding of the dipleg and the cyclone. This could result in high solids losses from the fluidized bed. Tests were conducted to demonstrate that cyclone diplegs …

Fast Pyrolysis Process Intensification: Study Of The Gas Phase Residence Time Distribution And Backmixing In A Downer Reactor, Martin Huard, Franco Berruti, Cedric Briens

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

A downer reactor was developed at ICFAR to maximize the liquid yield of pyrolysis in the conversion of biomass and heavy oil feedstock. An experimental study using hot wire anemometers was performed to measure the residence time distribution of the gas phase in the reactor and around the gas-solids separator. Some gas backmixing was observed around the gas-solids separator, which decreased with increasing distance between the separator and the gas outlet.

Hydrodynamics Of Conical Spouted Beds With High Density Particles, Salih Sari, Aylin Polat, Dokugan Zaglamaris, Gorkem Kulah, Murat Koksal

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

An extensive experimental investigation of conical spouted beds with high density particles were carried out by measuring bed pressure drop, particle velocity and solids hold-up in a 15 cm ID conical spouted bed at three different cone angles (30°, 45°, 60°) with Yttria-stabilized zirconia (YSZ) particles (ρp = 6050 kg/m3). The results show that the minimum external spouting velocity increases with cone angle, particle diameter and static bed height. The bed is characterized by two regions: upward moving particles with high slip in the spout and slowly downward moving particles at loosely packed conditions in the annulus.

Experimental Study On The Effects Of Gas Permeation Through Flat Membranes On The Hydrodynamics In Fluidized Beds, J.A.M. Kuipers, J.F. De Jong, M. Van Sint Annaland

10th International Conference on Circulating Fluidized Beds and Fluidization Technology - CFB-10

In this work, the effects of gas permeation through flat membranes on the hydrodynamics in a pseudo-2D membrane-assisted gas-solid fluidized bed have been investigated experimentally. A combination of the non-invasive Particle Image Velocimetry (PIV) and Digital Image Analysis (DIA) was employed to simultaneously investigate emulsion phase and bubble phase properties in great detail. Counter-intuitively, addition of secondary gas via the membranes, that constituted the confining walls of a gas-solid suspension at conditions close to incipient fluidization, did not result in a larger, but in a smaller bubble diameter, while gas extraction on the other hand, resulted in a larger equivalent …