Fluidization regimes in a conventional fluidized bed characterized by means of electrical capacitance tomography

Makkawi, Yassir; Wright, Phillip C.

doi:10.1016/s0009-2509(02)00138-0

Cited by 132 publications

(94 citation statements)

References 28 publications

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“…This can be explained considering that the air excess of case 2 e gives a regime transition from freely bubbling to turbulent flu idization. The regime transition for superficial velocities U 3U mf has been also reported by Makkawi and Wright [27]. Therefore, the proposed model K corrected,2D can be used when the fluidized bed is working in bubbling regime but not in turbulent fluidization.…”

Section: Effect Of the Superficial Gas Velocitysupporting

confidence: 65%

Gas interchange between bubble and emulsion phases in a 2D fluidized bed as revealed by two-fluid model simulations

Hernández-Jiménez

Gómez-García

Santana

et al. 2013

Chemical Engineering Journal

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Using two fluid model simulations, the present work aims at characterizing the interchange due to gas advection between the emulsion phase and bubbles in fully bubbling beds of Geldart group B particles that are fluidized with air. In the studied beds the bubbles are slow, which means that the advection transport of gas through the bubble boundary is the main mechanism of gas interchange. In an initial ver ification step, the pressure distribution and the gas interchange coefficient for isolated bubbles obtained in the two fluid simulation are compared with the classical potential flow theory of fluidized beds, pro viding concordant results. In a second step, the work analyzes the gas interchange in fully bubbling beds and the effects of the superficial velocity, bed height, and particle diameter on the interchange coefficient and the crossflow ratio. The results indicate that both the interchange coefficient and the crossflow ratio in bubbling beds are about two times those predicted by the potential theory of isolated bubbles. A cor rected model for the gas interchange is proposed based on the introduction of the gas throughflow into the classical potential flow theory. As a consequence, the gas interchange coefficient in the corrected model is a function of the superficial gas velocity instead of the minimum fluidization velocity.

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Section: Effect Of the Superficial Gas Velocitysupporting

confidence: 65%

Gas interchange between bubble and emulsion phases in a 2D fluidized bed as revealed by two-fluid model simulations

Hernández-Jiménez

Gómez-García

Santana

et al. 2013

Chemical Engineering Journal

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“…This makes it possible to obtain information about the solid fraction distribution within the bed at any given time. The average solid fraction value of the tower at each time step can also be calculated that can be used for statistical analyses of the bed behaviour [17,18].…”

Section: Solid Fraction Representationmentioning

confidence: 99%

A comparative study between electrical capacitance tomography and time-resolved X-ray tomography

Rautenbach

Mudde

Yang

et al. 2013

Flow Measurement and Instrumentation

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Modern day tomographs enable the research community to investigate the internal flow behaviour of a fluidized bed by non invasive methods that partially overcome the opaque nature of a dense bubbling bed. Each tomographic modality has its own limitations and advantages and in the present study two modern day tomographic systems were evaluated with respect to their performance on a cold dense fluidized bed. The two tomographs investigated are an Electrical Capacitance Tomography (ECT) tomograph and a time-resolved X-ray tomography tomograph. The study was performed on spherical glass particles with various particle size distributions that could mainly be classified as Geldart B or D particles. Two experimental towers were employed, one with a diameter of 10.4cm and the other 23.8cm while compressed air was used as fluidizing fluid during all of the experiments.Results obtained with both systems are provided in comprehensive figures and tables and some first results are obtained with the time-resolved X-ray tomography system. The bubble size measurements of both tomographs are compared with several theoretical correlations via the root mean square error of the predictions (RMSEP). With the results it was also concluded that a small amount of small particles can noticeably alter the fluidization hydrodynamics of a powder. The bubble frequencies are also presented to aid in understanding the hydrodynamic behaviour of the powders investigated. A comprehensive summary of the two tomographic modalities is also provided.

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“…The hydrodynamics of the bubbling and fast fluidization regimes are rather well understood, but interest in the turbulent regime has only strongly increased in the last two decades. Proper understanding of the flow structures in turbulent beds is still in its infancy with the initial investigations employing optical probes and Electrical Capacitance Tomography (ECT) techniques [5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…A very comprehensive ECT study is that of Makkawi and Wright, which spanned several regimes for a shallow bed [8,9]. Glass ballotini particles (Geldart B) were used for the bubbling, turbulent and fast fluidization regime and the aim was to define fluidization regimes based on these measurements.…”

Section: Introductionmentioning

confidence: 99%

Fast X-ray tomography for the quantification of the bubbling-, turbulent- and fast fluidization-flow regimes and void structures

Saayman

Nicol

Ommen

et al. 2013

Chemical Engineering Journal

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Fluidization regimes in a conventional fluidized bed characterized by means of electrical capacitance tomography

Cited by 132 publications

References 28 publications

Gas interchange between bubble and emulsion phases in a 2D fluidized bed as revealed by two-fluid model simulations

Gas interchange between bubble and emulsion phases in a 2D fluidized bed as revealed by two-fluid model simulations

A comparative study between electrical capacitance tomography and time-resolved X-ray tomography

Fast X-ray tomography for the quantification of the bubbling-, turbulent- and fast fluidization-flow regimes and void structures

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