Measurement of hydrodynamic data of gas-phase polymerization reactors using non-intrusive methods

Kantzas, Apostolos; Wright, Ian; Bhargava, Amit; Li, Fan; Hamilton, Kelly

doi:10.1016/s0920-5861(00)00523-x

Cited by 21 publications

(10 citation statements)

References 10 publications

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“…X-ray visualization has proven to be a useful and relatively inexpensive tool in providing good qualitative and quantitative data of dynamic behavior [16]. Successful measurements of time-average gas holdup have been made using these techniques [13,[17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging

Drake

Heindel

2012

Journal of Fluids Engineering

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Fluidized beds are common equipment in many process industries. Knowledge of the hydrodynamics within a fluidized bed on the local scale is important for the improvement of scale-up and process efficiencies. This knowledge is lacking due to limited observational technologies at the local scale. This paper uses X-ray computed tomography (CT) imaging to describe the local time-average gas holdup differences of annular hydrodynamic structures that arise through axisymmetric annular flow in a 10.2 cm and 15.2 cm diameter cold flow fluidized bed. The aeration scheme used is similar to that provided by a porous plate and hydrodynamic results can be directly compared. Geldart type B glass bead, ground walnut shell, and crushed corncob particles were studied at various superficial gas velocities. Assuming axisymmetry, the local 3D timeaverage gas holdup data acquired through X-ray CT imaging was averaged over concentric annuli, resulting in a 2D annular and time-average gas holdup map. These gas holdup maps show that four different types of annular hydrodynamic structures occur in the fluidized beds of this study: zones of (1) aeration jetting, (2) bubble coalescence, (3) bubble rise, and (4) particle shear. Changes in the superficial gas velocities, bed diameters, and bed material densities display changes in these zones. The 2D gas holdup maps provide a benchmark that can be used by computational fluid dynamic (CFD) users for the direct comparisons of 2D models, assuming axisymmetric annular flow.Keywords annular flow, fluidized bed, gas holdup, hydrodynamic structure, X-ray computed tomography Fluidized beds are common equipment in many process industries. Knowledge of the hydrodynamics within a fluidized bed on the local scale is important for the improvement of scale-up and process efficiencies. This knowledge is lacking due to limited observational technologies at the local scale. This paper uses X-ray computed tomography (CT) imaging to describe the local time-average gas holdup differences of annular hydrodynamic structures that arise through axisymmetric annular flow in a 10.2 cm and 15.2 cm diameter cold flow fluidized bed. The aeration scheme used is similar to that provided by a porous plate and hydrodynamic results can be directly compared. Geldart type B glass bead, ground walnut shell, and crushed corncob particles were studied at various superficial gas velocities. Assuming axisymmetry, the local 3D time-average gas holdup data acquired through X-ray CT imaging was averaged over concentric annuli, resulting in a 2D annular and time-average gas holdup map. These gas holdup maps show that four different types of annular hydrodynamic structures occur in the fluidized beds of this study: zones of (1) aeration jetting, (2) bubble coalescence, (3) bubble rise, and (4) particle shear. Changes in the superficial gas velocities, bed diameters, and bed material densities display changes in these zones. The 2D gas holdup maps provide a benchmark that can be used by computational fluid dynamic (CFD) users fo...

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Section: Introductionmentioning

confidence: 99%

Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging

Drake

Heindel

2012

Journal of Fluids Engineering

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“…Outside of these researchers, there are a few interested in the use of x-rays. The majority of the work is being done by Newton (Newton et al, 2001;Smith et al, 1995;Newton et al, 1994) and Kantzas (Zarabi and Kantzas, 1998;Wright et al, 2001;Kantzas et al, 2001;Kantzas, 1994;Holoboff et al, 1995). The main focus of the work conducted by these individuals is the behaviour of the gas phase in the solid beds, phenomena such as bubble growth and splitting, as well as the effect of gas distribution, temperature, and pressure.…”

Section: X-ray Imaging Techniquesmentioning

confidence: 99%

A Non-Invasive Hydrodynamic Study of Gas-Solid Fluidised Bed of Linear Low Density Polyethylene

Lee

Chandrasekaran

Hulme³

et al. 2008

Can. J. Chem. Eng.

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G as-solid fl uidised bed reactors are used for a variety of industrial applications ranging from coal gasifi cation to polymer and pharmaceutical production. Despite this widespread usage, gas-solid fl uidised column design is based on heuristics and on the behaviour of costly large-scale pilot plants. Such methods may lead to poor design of the reactor unit, which in turn can lead to diffi culties in operation and control, lost time, lost energy and poor effi ciency. By studying the hydrodynamic complexities of small-scale reactors it is hoped that steps, such as the construction and operation of large-scale models, can be optimised or even eliminated. Fluidised beds could then be designed based on fi rst principles, small scale experiments and CFD (Computational Fluid Dynamics) models based on experimental data from small scale units.In our laboratory, we have developed and used non-invasive measurement techniques such as multiple radioactive particle tracking (MRPT), digital fl uoroscopy (DF), computed tomography (CT) and wall pressure fl uctuations to examine fl ow phenomena of two-phase (air-solid) beds (Zarabi MEG Worley, Calgary, AB MEG Worley, Calgary, ABThere are several non-invasive techniques used to study the hydrodynamic characteristics of gas-solid fl uidised bed reactors. In this study a two phase, gas-solid fl uidised bed consisting of air and a linear low-density polyethylene (LLDPE) resin was examined. The polyethylene sample was composed of irregular, non-monosized particles ranging in size from 165 to 1500 µm. The experimental techniques used were digital fl uoroscopy and pressure fl uctuations. This study presents a comparison of the two-phase system experimental results and two-dimensional CFD simulation results. CFD packages FLUENT and MFIX were used.

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“…The spatial resolution of X-ray tomography is very high. Kantzas et al (1996Kantzas et al ( , 1997Kantzas et al ( , 2001 obtained images of the density and holdup using a modifi ed medical scanner. Although the spatial resolution of this system was high, it took usually over 1 s to scan one slice of the column.…”

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confidence: 99%

Observation of 3-D Structure of Bubbles in a Fluidized Catalyst Bed

et al. 2008

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The interface area between the bubble and emulsion phases in a fluidized catalyst bed is one of the important parameters used to analyze and design the fluidized bed reactor. We used a fast‐scanning X‐ray CT system to observe the bubble shape and structure. We then obtained the transient 2‐dimensional cross sectional gas‐phase distribution in a fluidized catalyst bed. Using image‐processing techniques, pseudo 3‐dimensional images of the bubbles were reconstructed. The bubble structure was studied based on the 3‐dimensional images and the previously obtained results in a 2‐dimensional fluidized bed. It was found that the bubble shape was not spherical but complicated, and that the bubbles ascending in a fluidized catalyst bed consisted of some smaller bubbles.

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Measurement of hydrodynamic data of gas-phase polymerization reactors using non-intrusive methods

Cited by 21 publications

References 10 publications

Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging

Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging

A Non-Invasive Hydrodynamic Study of Gas-Solid Fluidised Bed of Linear Low Density Polyethylene

Observation of 3-D Structure of Bubbles in a Fluidized Catalyst Bed

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