Dynamics of segregation and fluidization of binary mixtures in a cylindrical fluidized bed

Singh, Brajesh K.; Roy, Shantanu; Buwa, Vivek V.

doi:10.1002/aic.16682

Cited by 15 publications

(22 citation statements)

References 26 publications

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“…The segregation percentage decreased as the sand particle size decreased, and the sisal residue particle size increased. This result is not in line with the work of Singh et al [29], which showed that the smallest particle size contributes to a well-mixed bed.…”

Section: Segregation Behaviorcontrasting

confidence: 99%

Study of The Biomass, Sand, and Biochar Fluidization in A Typical Bed of Fast Pyrolysis

Vasconcelos

Júnior

Simonelli

et al. 2021

Preprint

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Biomass pyrolysis usually occurs in a fluidized bed reactor formed by sand, biomass, and biochar. Dynamics this fluidization differs from that of literature because the biomass is converted continually in biochar. In this study, a series of experiments have been carried out for ternary mixtures of sand, sisal residue, and biochar, varying the compositions and particle size. The tests were based on two simplification hypotheses (steady state and room temperature) due to fast biomass transformation in bed and low Van der Waals force to large particles. The dynamic characteristics determined included the bed pressure drop and bed fluctuation. The single and combined effects of particle size and composition on the final fluidization velocity (Uff) and particle segregation (S) have been analyzed using response surface (RSM). The Uff and S minimum values were found when the variables were in the smallest particle size and composition levels. New correlations were developed for predicting the values of Uff. The error from measured values when using the new correlation was 7.6%, while the literature equation was 9.7%. The present correlations predicted reasonably well predicted the Uff of ternary mixtures in the fast pyrolysis bed.

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Section: Segregation Behaviorcontrasting

confidence: 99%

Study of The Biomass, Sand, and Biochar Fluidization in A Typical Bed of Fast Pyrolysis

Vasconcelos

Júnior

Simonelli

et al. 2021

Preprint

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“…A comparison of measured and predicted particle dispersion heights (bed expansion) for Geldart Group-B (G922) and Group-A (G96) particles is shown in Figure . A high-speed photographic imaging technique was used to measure the particle dispersion heights . The spread bars shown on the measured and predicted dispersion heights at different U G represent the maximum and minimum dispersion heights.…”

Section: Results and Discussionmentioning

confidence: 99%

“…The instantaneous change in the α s distributions over the bed cross section was measured using ECT at an axial height of z = 24 cm from the distributor plate. From the measured α s distributions, the time evolution of α s distributions along the diameter of the bed was extracted and is shown in Figure a . A similar methodology was used to calculate the time evolution of α s distributions from the simulations data (Figure b–d).…”

Section: Results and Discussionmentioning

confidence: 99%

“…The time evolution of the horizontal chord length ( d h ) was used to calculate the bubble sizes; the maximum d h for a particular bubble was referred to as the horizontal bubble size of that bubble. The measured horizontal bubble size distribution for G922 particles at U G = 0.9 m/s reported in our earlier work was used to validate the corresponding predictions (see Figure a). The size of the bubbles was seen to be large ( d h > 6 cm) and the maximum size of the bubbles was found to reach 9 cm, which is equal to the internal diameter of the bed.…”

Section: Results and Discussionmentioning

confidence: 99%

“…The Eulerian two-fluid model was used to simulate unsteady gas–solid flow in the cylindrical fluidized bed with the geometry same as that used in the previous work . The gas-phase and solid-phase continuity equations (eqs and ) and momentum equations (eqs and ) are given in Table .…”

Section: Numerical Simulationsmentioning

confidence: 99%

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Eulerian Simulations of Bubbling Behavior in a Gas–Solid Fluidized Bed: Role of Solid Frictional Viscosity

Singh

Roy

Buwa

2021

Ind. Eng. Chem. Res.

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Eulerian computational fluid dynamics (CFD) models that can predict bubbling behavior accurately are important to predict solids mixing, transport processes, and reactions in fluidized beds. In the present work, Eulerian two-fluid simulations are performed to understand the role of solid-phase viscosity in bubbling behavior for different Geldart Group particles and in the entire bubbling regime. The predictions are validated with temporally and spatially resolved measurements performed using electrical capacitance tomography (ECT). In dense conditions, the solid frictional viscosity around the bubbles was higher and the gas tends to accumulate in the bubbles, leading to the formation of larger bubbles. However, under dilute conditions, smaller bubbles are formed due to the marginal influence of the frictional viscosity. Further, the bubbling frequency and bubble chord length distribution predicted using the Johnson−Jackson frictional pressure model with a critical solid volume fraction of 0.55 and the Schaffer frictional viscosity model are in good agreement with the corresponding ECT measurements.

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Particle velocity measurement of binary mixtures in the riser of a circulating fluidized bed by the combined use of electrostatic sensing and high-speed imaging

et al. 2020

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The flow dynamics of binary particle mixtures in the fluidized bed needs to be monitored in order to optimize the related industrial processes. In this paper, electrostatic sensing and high-speed imaging are applied to measure the velocities of polyethylene and sand particles in the binary particle mixtures in fluidization. Experimental studies were conducted on a lab-scale cold circulating fluidized bed. Correlation function between electrostatic signals from upstream and downstream electrodes placed along the riser shows two peaks that represent transit times for the two types of particles. To verify the above results, high-speed imaging was adopted to capture the flow images of particle mixtures. Particle Image Velocimetry and Particle Tracking Velocimetry algorithms were utilized to process the resulted images in order to measure the velocities of polyethylene and sand particles. The reasons for two-peak correlation functions are illustrated based on the frequency spectrums of the mono-solid-phase electrostatic signals and the velocity difference between polyethylene and sand particles. Finally, comparisons on the velocities obtained from electrostatic sensing and high-speed imaging demonstrate the electrostatic sensor can roughly estimate the particle velocity of binary particle mixtures in the near wall region of the circulating fluidized bed. Keywords Binary mixtures • Fluidized bed • Electrostatic sensor • High-speed imaging Abbreviations ADC Analog to digital converter BFB Bubbling fluidized bed CFB Circulating fluidized bed DCC Direct cross-correlation ECT Electrical capacitance tomography FFT Fast fourier transform PE Polyethylene PIV Particle image velocimetry PTV Particle tracking velocimetry RPT Radioactive particle tracking List of symbols C(d) Cross-correlation coefficient f(x, y) Gray distribution of the binary image L Distance between the upstream and the downstream electrodes, m m pq 2-D moment of order (p + q) n Strictness of the filter S 1 (z 1, t) Upstream electrostatic signals, V S 2 (z 2, t) Downstream electrostatic signals, V S PE (t) Components from PE particles, V S sand (t) Components from sand particles, V T Integral time, s t lower Lower velocity threshold, m/s t upper Upper velocity threshold, m/s u Mean velocity, m/s x X coordinates of the centroid y Y coordinates of the centroid Edited by Xiu-Qiu Peng

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Dynamics of segregation and fluidization of binary mixtures in a cylindrical fluidized bed

Cited by 15 publications

References 26 publications

Study of The Biomass, Sand, and Biochar Fluidization in A Typical Bed of Fast Pyrolysis

Study of The Biomass, Sand, and Biochar Fluidization in A Typical Bed of Fast Pyrolysis

Eulerian Simulations of Bubbling Behavior in a Gas–Solid Fluidized Bed: Role of Solid Frictional Viscosity

Particle velocity measurement of binary mixtures in the riser of a circulating fluidized bed by the combined use of electrostatic sensing and high-speed imaging

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