A novel approach for modeling bubbling gas-solid fluidized beds

Briongos, Javier Villa; Sánchez-Delgado, S.; Acosta-Iborra, A.; Santana, D.

doi:10.1002/aic.12375

Cited by 9 publications

(3 citation statements)

References 48 publications

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“…The activation region, h min , is defined as the minimum height at which the particle movement is promoted due to the presence of the bubbles [16]. In this work a value of h min = 0.05 m guarantees the presence of bubbles in the fluidized bed for all of the cases.…”

Section: Experimental Circulation Timementioning

confidence: 99%

Estimation and experimental validation of the circulation time in a 2D gas–solid fluidized beds

et al. 2013

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Abstract:The circulation time is defined as the time required for a group of particles to reach the freeboard from the bottom of a fluidized bed and return to their original height. This work presents an estimation and validation of the circulation time in a 2D gas solid bubbling fluidized bed under different operating conditions. The circulation time is based on the concept of the turnover time, which was previously defined by Geldart [1] as the time required to turn the bed over once. The equation t c,est = 2 Ah′/Q b is used to calculate the circulation time, where A is the cross section of the fluidized bed, h′ is the effective fluidized bed height and Q b is the visible bubble flow. The estimation of the circulation time is based on the operating parameters and the bub ble phase properties, including the bubble diameter, bubble velocity and bed expansion. The experiments for the validation were carried out in a 2D bubbling fluidized bed. The dense phase velocity was measured with a high speed camera and non intrusive techniques such as particle image velocimetry (PIV) and digital image analysis (DIA), and the experimental circulation time was calculated for all cases. The agreement between the theoretical and experimental circulation times was satisfactory, and hence, the proposed estimation can be used to reliably predict the circulation time.

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Section: Experimental Circulation Timementioning

confidence: 99%

Estimation and experimental validation of the circulation time in a 2D gas–solid fluidized beds

et al. 2013

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“…In some previous DBM works [3,4,7,8] a sudden coalescence approach was used whenever two bubbles touched each other, and in some other studies the coalescence was not considered a sudden phenomena [20,21]. In the present work, a delayed coalescence method, such as that presented by Movahedirad et al [5,6], was used.…”

Section: Coalescence Of the Bubblesmentioning

confidence: 94%

A Novel Model for Predicting the Dense Phase Behavior of 3D Gas‐Solid Fluidized Beds

Movahedirad¹,

Ghafari²,

Dehkordi³

2013

Chem Eng & Technol

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A novel phenomenological discrete bubble model was developed and tested for prediction of the hydrodynamic behavior of the dense phase of a 3D gas-solid cylindrical fluidized bed. The mirror image technique was applied to take into account the effects of the bed wall. The simulation results were validated against experimental data reported in the literature that were obtained by positron emission particle tracking. The time-averaged velocity profiles of particles predicted by the developed model were found to agree well with experimental data. The initial bubble diameter had no significant influence on the time-averaged circulating pattern of solids in the bed. The model predictions clearly indicate that the developed model can fairly predict the hydrodynamic behavior of the dense phase of 3D gas-solid cylindrical fluidized beds. IntroductionGas-solid fluidized beds are widely used in chemical industries as reactor or contactor, e.g., [1,2]. In the bubbling regime of gas-solid fluidized beds, bubbles play the main role in the solids mixing. Thus, gas bubbles are key factors in the hydrodynamics of these contactor devices together with heat and mass transfer rates and the fractional conversion of chemical reactions in gas-solid fluidized beds.Because of the importance of simulation and its advantages over experimental works, it is essential to develop new simple models for simulation of gas-solid fluidized beds. It is difficult to model the gas bubble behavior in the presence of other bubbles because of the chaotic nature of gas-solid fluidized beds and continuous changes of the shape of gas bubbles. In this regard, the discrete bubble model (DBM) is a simple approach for prediction of the gas bubble behavior in gas-solid fluidized beds [2][3][4][5][6]. In this modeling approach, each bubble is individually tracked with time. The bubble velocity can vary as a result of the interaction of other bubbles present in the bed.Bokkers et al. [3] developed a DBM to model large-scale fluidized beds. They used the techniques of computational fluid dynamics (CFD) to predict the emulsion-phase flow patterns. Later, this model was extended to account for the effects of bubble-bubble interactions [4]. Pannala et al. [7,8] described a dynamic interacting bubble simulation (DIBS) for ozone decomposition in a gas-solid fluidized bed. Although their model is a DBM, they did not focus on the solid circulation patterns in the bed. Movahedirad et al. [6] studied the bubble phase behavior of 3D gas-solid fluidized beds using the bubble-bubble interaction model presented by Clift and Grace [9]. In our previous work, it was demonstrated that the binary interaction model used in the DIBS by Pannala et al. [7,8] cannot be an appropriate approach to treat bubbles in freely gassolid bubbling fluidized beds (FBFBs) [6]. In addition, a neighbor list of bubbles influencing a gas bubble in an FBFB was used.Kobayashi et al.[10] developed a numerical model to evaluate the gas bubble distribution and the circulation pattern of the solids in FBFBs...

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“…Some recent developments reveals the importance of the coupling between gas and solid phase to successfully represent the physics behind the fluidized bed dynamics in pulsating flows (Wu et al, 2017) and the importance of distributor performance on the effectiveness of the fluidization (Kanholy et al, 2017). On the other hand, the discrete bubble model approach (Bokkers et al, 2006;Briongos et al, 2011;Pannala et al, 2004) tries to answer the long-term behavior of gas-solid fluidized beds by direct modeling the bubbling phenomena observed. However, in order to speed up the solution process and to focus on the long-term information, a better understanding of the bubble generation process to measure the distributor effect on the bed dynamics becomes crucial, having a significant impact on the computational cost of the bubble generation modelling.…”

Section: Introductionmentioning

confidence: 99%

Distributor performance in a bubbling fluidized bed: Effects of multiple gas inlet jet and bubble generation

Sánchez-Delgado

Marugán-Cruz

Serrano

et al. 2019

Chemical Engineering Science

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This work presents a study of the effect of the distributor performance in the bubble generation, growth and interaction within a bubbling fluidized bed. In order to characterize this effect in short-term and long-term dynamics, as well as in time and frequency domain, classical and innovative techniques (Digital Image Analysis, DIA, and Wavelet Analysis WA, respectively) have been used over the images acquired in a two dimensional bubbling fluidized bed.Four perforated plate distributors, with the same open area and the same pressure drop, have been used in the experiments, varying the excess gas and the fixed bed height to study the effect of this operation conditions. The results reveal that the distributor performance has no effect in the mean bubble behavior of the bubbles within the fluidized bed, and therefore there is no effect in the long-term dynamics of the fluidized bed. The analysis, performed on the bubble generation region, also reveals that the distributor as no effect on the bubble generation frequency. However, it can be concluded that distributor performance has a great influence in the bubble generation location along the distributor, being the most homogenously distributed generation profiles, those in which the distributor with the largest numbers of holes and smaller diameter has been used. The distributor affects importantly the total number of bubbles (the higher the number of holes the more bubbles are generated). The fixed bed height does not affect the PDF (Probability Density Function) of the bubbles along the distributor, however the PDF of the bubbles along the distributor presents more homogenous profiles at higher values of the excess gas. These results reveal the great importance of the distributor type in the modelling of bubbling phenomena, but only in the bubble generation region, since from this region the fluidized bed dynamics is not affected for the distributor type.

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A novel approach for modeling bubbling gas-solid fluidized beds

Cited by 9 publications

References 48 publications

Estimation and experimental validation of the circulation time in a 2D gas–solid fluidized beds

Estimation and experimental validation of the circulation time in a 2D gas–solid fluidized beds

A Novel Model for Predicting the Dense Phase Behavior of 3D Gas‐Solid Fluidized Beds

Distributor performance in a bubbling fluidized bed: Effects of multiple gas inlet jet and bubble generation

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