Engineering Commons^™

Role Of Intrinsic Kinetics And Catalyst Particle Size Distribution In Cfd Simulations Of Polymerization Reactors, Rong Fan, Rodney O. Fox, Michael E. Muhle

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

Fluidized-bed reactors are widely used in the production of polyethylene. In this work, the quadrature method of moments (QMOM), a chemical reaction engineering (CRE) model, and computational fluid dynamics (CFD) are combined to investigate the role of intrinsic kinetics and the catalyst particle size distribution (PSD) in a gas phase fluidized bed reactor. The catalyst PSD is represented by a few nodes using the QMOM and an intrinsic rate model based on the age of particles is used to solve the evolution of particle temperature, particle size, and catalyst sites with age. Assuming the particle age distribution is well-mixed, the …

Particle Size Distribution In Gas-Phase Polyethylene Reactors, Omid Ashrafi, Navid Mostoufi, Rahmat Sotudeh-Gharebagh

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

A population balance model is developed to investigate the particle-size distribution developments in a gas-phase fluidized-bed ethylene polymerization reactor. The model considers the combined effects of particle growth and elutriation for size distributed prepolymer feed. In the proposed model, the bed is divided into several sections consisting of bubble and emulsion phases. The population balance differential equations derived for each section were simultaneously solved to determine the density function of the size distribution of the polymer particles in each section. The model is able to predict the axial profiles of particle size distribution. It was also shown that the mean …

Volume Contraction In Liquid Fluidization Of Binary Solids Mixtures, Norman Epstein , R. Escudié, John R. Grace, Xiaotao T. Bi

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

When liquid-fluidized particles of radically different sizes and densities mix, the serial (additive volume) model fails to predict the fluidized bed voidage due to contraction of the mixed bed relative to the volumetric sum of the corresponding monocomponent beds. Models are proposed to predict contraction reported in the literature for both upflow and downflow fluidization.

Hydrodynamics Of Gas-Solids Bubbling Fluidized Beds Using Polyethylene Resin, Bangyou Wu, John Shepperson, Loni Van Der Lee, Céline Bellehumeur, Apostolos Kantzas

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

Pressure fluctuations were measured in three gas-solids bubbling fluidized beds (10cm, 20cm, and 30cm diameter, 1.0m high) using polyethylene particles of different sizes and particle size distributions. Both bed scale and particle size distribution significantly affect the gas-solids flow behavior. Bubble diameters measured from X-ray fluoroscopy in the 10cm diameter column were compared to various correlations in the literature.

Monitoring Electrostatic Charges In Fluidized Beds, Xiaotao T. Bi, Aihua Chen, John R. Grace

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

A novel analysis procedure for dynamic collision probes has been developed to monitor the charge density of particles in gas-solids fluidized beds based on the mean and normalized standard deviation of current signals. The contribution from hydrodynamic changes is decoupled from the changes in specific particle charge density based on the principles that the average current is related to charge transfer and/or triboelectrification due to the contact between the probe and particles, whereas the normalized standard deviation of current signals is mainly related to the hydrodynamic changes of the fluidized bed. The correlation between hydrodynamic changes and current signal fluctuations …

The Measurement Of Thermal Performance For A Fluidized Bed, H. R. Goshayshi

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

Abstract Experiments have been performed to measure the thermal performance, packed density, and velocity of a fluidized bed cooling tower of 280 mm diameter.

Hollow plastic spheres of three different sizes, with diameters of 20, 25 and 37 mm and particle densities ranging from 70 to 325 kg/m3 were investigated as packing materials, and results for static bed heights of 100 mm and 300 mm are reported. Measurements were obtained at an approximately constant inlet hot water temperature of around 42°C and cover a range of water mass flux from 0.3 to 3.6 kg/sm2. Liquid/gas ratios varied between 0.1 and …

Towards Selective Agglomeration Detection In Fluidized Beds Using Advanced Signal Analysis Methods, Malte Bartels, Bart Vermeer, John Nijenhuis, Ruud Van Ommen, Freek Kapteijn

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

A new methodology of assessing large amounts of fluidized bed pressure fluctuation data with various signal analysis methods in combination with signal pre-treatment methods is presented. This approach can be used to find certain combinations that are selectively sensitive to certain physical effects in fluidized beds, such as agglomeration.

Investigation Of The Sources Of Variability In The Wurster Coater: Analysis Of Particle Cycle Times Using Pept , Sarah Palmer, Andy Ingram, Xianfeng Fan, Shaun Fitzpatrick, Jonathan Seville

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

Positron Emission Particle Tracking (PEPT) has been used successfully to study pellet motion within the Wurster coater. PEPT experiments were undertaken to understand how the parameters of batch size and partition gap interact with each other; and to determine their effects on the particle cycle time and the components of the particle cycle time: the flight and annulus times and their respective distributions. This enabled the determination of optimum operating conditions for a given set of process conditions.

Laser Diagnostics Of Hydrodynamics And Gas-Mixing In The Splash Zone Of Gas-Fluidized Beds, Roberto Solimene, Antonio Marzocchella, Raffaele Ragucci, Piero Salatino

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

The hydrodynamic patterns of gas flow associated with bubbles bursting at the surface of gas-fluidized beds have been investigated by means of planar laser induced fluorescence using acetone as diffusive gas tracer. The flow structures generated by the eruption of an isolated bubble have been characterized as a function of bed material size and of bubble injection level.

Particle Size Estimation And Monitoring In A Bubbling Fluidized Bed Using Pressure Fluctuation Measurements, Clive Davies, Donal Krouse, Alison Carroll

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

Pressure time data for binary mixtures of silica sand have been examined with particular reference to correlation between mean particle size, standard deviation and parameters obtained through attractor reconstruction techniques. The ratio of total variance to high speed variance is a particularly useful parameter for regime identification.

Development Of Electrical Capacitance Volume Tomography (Ecvt) And Electrostatic Tomography (Est) For 3d Density Imaging Of Fluidized Bed System, B. Du, Q. Marashdeh, W. Warsito, A.-H. A. Park, L S Fan

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

In this paper, Electrical Capacitance Volume Tomography (ECVT) is used to study a gas-solid fluidized bed system of .1 m ID. The interior flow structures (including the dynamic bed expansion, bubble/void breakage and particle movement) and the charge distribution in a gas-solid fluidized bed are illustrated based on the 3D images obtained from the ECVT.

X-Ray Fluoroscopy Measurements And Cfd Simulation Of Hydrodynamics In A Two Dimensional Gas-Solids Fluidized Bed, Zhengxing He, Bangyou Wu, Blake Chandrasekaran, Celine Bellehumeur, Apostolos Kantzas

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

X-ray fluoroscopy measurements and CFD simulation were used to characterize the hydrodynamics in a pseudo 2-D gas-solids bubbling fluidized bed using polyethylene resin and glass beads. Bubble properties, such as bubble frequency, bubble size, bubble number distribution and bubble diameter distribution, were estimated from X-ray images and compared to those from CFD simulation.

Microfluidic Velocity Measurements Using Three-Dimensional Confocal Micro Particle Tracking Velocimetry (Cm-Ptv), Orin Hemminger, Zhao Yu, Chunhe Zhang, L. James Lee, L .S. Fan

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

In the past, confocal microscopy was limited by its slow temporal resolution and was not a practical tool for imaging dynamic systems. Recent improvements in spinning disk confocal microscopy and high-speed camera technology have made it a viable technique for imaging of microfluidic systems. Here, a confocal micro particle tracking velocimetry (CM-PTV) system is demonstrated with the ability to obtain 3D velocity profiles at high flow rates.

Scale-Up Effect On Heat Transfer In A Fluidized Bed Near The Onset Of Turbulent Fluidization, A. Stefanova, John R. Grace, C. Jim Lim, Xiaotao T. Bi, K.S. Lim, J. Sanderson

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

Heat transfer coefficients were measured in 0.29 m ID and 1.56 m ID fluidization columns with the same heater tube, identical alumina particles and geometrically scaled distributors. The maximum coefficients occurred in the turbulent fluidization flow regime. The Froude number based on superficial velocity and column diameter captures the scale-up effect well, so long as the heater is located in a region of similar flow structure.

Hydrodynamic Aspects And Correlations For The Design Of Draft-Tube Conical Spouted Beds, H. Altzibar, S. Alvarez, M.J. San José, R. Aguado, J. Bilbao, Martin Olazar

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

A study has been carried out on the hydrodynamics of conical spouted beds with draft tube. Correlations have been proposed for calculating minimum spouting velocity, operating pressure drop and peak pressure drop as functions of dimensionless module that take into account geometric factors, particle characteristics and operating conditions.

Portable Positron Emission Particle Tracking (Pept) For Industrial Use, A. Ingram, M. Hausard, X. Fan, D. J. Parker, J.P.K. Seville, N. Finn , M. Evans

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

Positron Emission Particle Tracking (PEPT) has over the last decade become an established technique for studying the motion of particles in granular and fluid systems. Until recently, this technique was confined to use with medically-derived cameras that have fixed limits in terms of the size and position of the field of view. This provides some constraints on the geometry and scale of process equipment that can be viewed. Increasing demand for greater flexibility in the use of the PEPT technique - in larger process equipment and, more importantly, in industrial equipment in situ - has led to the development of …

Discrete Particle Simulation Of The Gas-Solid Flow In A Circulating Fluidized Bed, K. W. Chu, B. Wang, Aibing Yu

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

This paper presents a numerical study of the gas-solid flow in a three-dimensional Circulating Fluidized Bed (CFB) by means of Combined Continuum and Discrete Method (CCDM) in which the motion of discrete particles is described by Discrete Particle Method (DPM) on the basis of Newton’s laws of motion applied to individual particles and the flow of continuum fluid by the traditional Computational Fluid Dynamics (CFD) based on the local averaged Navier-Stokes equations. The simulation is achieved by incorporating DPM codes into the commercial CFD software package Fluent. It is shown that the discrete particle simulation can capture the key flow …

Simulation Of A Silicon Cvd Spouted Fluidized Bed Reactor: Semi-Batch Operations, Juliana Piña, Verónica Bucalá, Susana N. Schbib, Paul Ege, Hugo Ignacio De Lasa

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

A comprehensive multiphase gas-solid mathematical model that successfully describes the batch growth of silicon particles in a chemical vapor deposition (CVD) submerged spouted bed reactor is extended to simulate semi-batch operations with periodic seeds additions and product extractions. This model takes into account the fluidized bed reactor as well as a population balance equation representing particle growth and agglomeration. Experimental data obtained from semi-batch operation in a pilot scale reactor at REC Silicon Inc. are used to evaluate the proposed mathematical model.

In Situ Measurement Of Dynamic Mixing In Gas-Solid Fluidized Beds Using Magnetic Resonance, D. J. Holland, P. S. Fennell, C. R. Müller, J. S. Dennis, L. F. Gladden, A. J. Sederman

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

Three magnetic resonance techniques were implemented to study solids mixing in a fluidized bed. Ultra-fast FLASH imaging was utilised to measure the dispersion of a tracer particle in real time. A novel MR sequence for measurement of the time-averaged mixing of solids in a fluidized bed was developed. Finally images of the velocity of solids were obtained to measure directly the pattern of solids flow.

Experimental Validation Of Macro- And Micro-Level Scaling Laws In Small- And Medium-Scale Top-Spray Fluidised Bed Coaters, Peter Dybdahl Hede, Poul Bach, Anker D. Jensen

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

Top-spray fluid bed coating experiments of 500 g sodium sulphate cores (180 – 300 μm) have been conducted in a small-scale single-spray nozzle GEA Strea-1 fluid bed. The process has been scaled-up to a bed load of 4 kilos in a single-spray nozzle Niro MP-1 fluid bed testing different scaling laws for comparison. Results indicate clearly that up-scaling using a drying force parameter (combining bed temperature with bed relative humidity) as well as a droplet related relative parameter is a promising alternative to common fluid bed scaling principles.

Time Scale Analysis Of A Fluidized-Bed Catalytic Reactor Based On A Generalized Dynamic Model, Andres Mahecha-Botero, John R. Grace, Said S.E.H. Elnashaie, C. Jim Lim

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

A fluidized-bed reactor model is implemented to simulate a Maleic Anhydride (MA) reactor with special emphasis on its dynamic behaviour. The dynamic model is general enough that it can treat a wide range of catalytic systems, subject to mass and energy balances within the phases. The model represents multiple phases and regions (low-density phase, high-density phase, freeboard region) and can account for heat and mass axial and radial anisotropic dispersion, change in molar/volumetric flow due to reaction, temperature and pressure profiles, hydrodynamic regime variation, catalyst deactivation, energy options, and multiple membranes of various geometries for introduction/extraction of any compound. The …

Radial Distribution Of Particle Clusters In Down Flow Reactors, Samuel R. Nova, Stefan Krol, Hugo Ignacio De Lasa

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

Particle clustering is of major importance in down flow reactors having a profound influence on some fundamental properties of the flowing suspension such as particle slip velocity. The goal of this study is to provide further evidence to support the formation of clusters using the novel CREC-GS-Optiprobes. This sensor is equipped with GRIN lenses and introduces minimum intrusion effects. Results reported include radial distributions of particle cluster size and velocity under various gas flow superficial velocities and suspension densities. Micro-scale and macro-scale flow structures are advanced on the basis of the reported data.

Effect Of Horizontal Passage Length On Solid Recycle Through A Loop Seal In A Circulating Fluidized Bed, James W. Butler, Prabir Basu

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

Solid flow through the loop seal of a circulating fluidized bed (CFB) was studied by investigating the effect of the horizontal passage length on solid flow through the loop seal. This was done by investigating the effects of aeration on the inter-particle friction forces, the effect varying horizontal passage lengths had on the overall solid flux around the CFB loop and on the pressure drop across the passage. The division of air flow through the loop seal was also investigated in order to determine how the solids were driven through the loop seal. It was found that for a measurable …

Drying Of Moist Solid Particulate In A Bubbling Fluidised Bed, Yassir Makkawi, Jamie Duncan, Marc Mcandrew, Raffaella Ocone

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

Air at ambient conditions was used to dry moist particles at various fluidisation velocities. Throughout the drying process, images of the material distribution were recorded using Electrical Capacitance Tomography (ECT). Simultaneously, the outlet air moisture content was measured using temperature/humidity probe. The ECT data were used to quantify the bubbles characteristics while the air moisture content was used to calculate the drying rate. To avoid the complexity of the process, the fluidised bed was operated at single bubbling regime. The experimental results are discussed in relation to the different drying mechanisms.

Waste Edible Oil Fluid Catalytic Cracking In A Downer Reactor, Xiaoping Tang, Fei Wei

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

The waste edible oil fluid catalytic cracking process (FCC), an environment friendly process to produce clean fuel (such as gasoline, diesel) and high-value chemical materials (such as propylene), was studied in an small hot model of downer reactor under the temperature 500 ℃, the pressure 1.1×105Pa , the resident time 1 second, the ratio of catalyst to oil 12 , and MA-83 as the catalyst. Compared with other processes, the waste edible oil FCC process can realize the waster utilizing and adjust the product distribution according to the market demand, while with a convenient pretreatment to the raw materials. The …

Simulation Of A Pulsating Bed Using Eulerian Approach, Shyam Shankar Dokka, Hamid Arastoopour

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

A numerical study of the effect of gas pulsation on the flow pattern of solid particles in a two-dimensional gas-solid fluidized bed was conducted using the Eulerian granular kinetic theory. Our simulated bed dynamics agreed well with the experimental work of Koksal and Vural, and with the Discrete Element Method (DEM) model simulations of Tsuji et al.

A Discrete Particle Simulation Study Of Solids Mixing In A Pressurized Fluidized Bed, Willem Godlieb, Niels G. Deen, J.A.M. Kuipers

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

A fluidized bed containing polymeric particles is investigated using a state-of-the-art soft-sphere discrete particle model (DPM). The pressure dependency of particle mixing, flow patterns and bubble behaviour are analysed. It is found that with increasing pressure a less distinct bubble-emulsion structure and improved solids mixing can be observed.

Approximate Prediction Of Gas-Solid Conversion In Fluidized Bed Reactors, Alberto Gómez Barea, B. Leckner, M. Campoy

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

A simple method is proposed to evaluate the performance of fluidized bed reactors where an nth-order gas-solid reaction occurs. The method takes into account the fluid dynamics of the fluidized bed by a two-phase flow model and the rates of diffusion in the solid reactant particles (internal and external) by a simple particle model. Approximate analytical expressions are derived in terms of three effectiveness factors: interphasic, external and intraparticle. These account for the contribution of fluid-dynamic and diffusional resistances to the overall mass-transfer resistance. Gas conversion is expressed in terms of four dimensionless governing quantities and the reaction order, in …

A Rotating Fluidized Bed In A Static Geometry: Experimental Proof Of Concept, Juray De Wilde, Luc Wautier, Guy B. Marin, Geraldine J. Heynderickx, Axel De Broqueville

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

The new concept of a rotating fluidized bed in a static geometry (RFB-SG) is presented (1). The rotating motion of the particle bed and the tangential fluidization of the solids are obtained by the tangential injection of the fluidization gas via multiple gas inlet slots in the outer cylindrical wall of the fluidization chamber. The new fluidization concept is experimentally investigated and proven using either large diameter, low density polymer particles or small diameter, higher density Alumina particles.

Influence Of Bubble-Bubble Interactions On The Macroscale Circulation Patterns In A Bubbling Gas-Solid Fluidized Bed, J. A. Laverman, M. Van Sint Annaland, J.A.M. Kuipers

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

The macro-scale circulation patterns in the emulsion phase of a gas-solid fluidized bed in the bubbling regime have been studied with a 3D Discrete Bubble Model. It has been shown that bubble-bubble interactions strongly influence the extent of the solids circulation and the bubble size distribution.