Computational study of the bubbling-to-slugging transition in a laboratory-scale fluidized bed

doi:10.1016/j.cej.2016.08.113

Chemical Engineering Journal

Volume 308, 15 January 2017, Pages 544-556

https://doi.org/10.1016/j.cej.2016.08.113 Get rights and content

Highlights

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The bubbling to slugging transition occurs over a range of gas flow.
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Unique spatiotemporal features emerge in the bubbling-to-slugging transition.
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High-speed pressure measurements respond to unique spatiotemporal features.
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Bubbling-to-slugging transition spatiotemporal features vary with axial location.
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On-line bubbling-to-slugging transition diagnostic development with a model.

Abstract

We report results from a computational study of the transition from bubbling to slugging in a laboratory-scale fluidized-bed reactor with Geldart Group B glass particles. For simulating the three-dimensional fluidized-bed hydrodynamics, we employ MFiX, a widely studied multi-phase flow simulation tool, that uses a two-fluid Eulerian-Eulerian approximation of the particle and gas dynamics over a range of gas flows. We also utilize a previously published algorithm to generate bubble statistics that can be correlated with pressure fluctuations to reveal previously unreported details about the stages through which the hydrodynamics progress during the bubbling-to-slugging transition. We expect this new information will lead to improved approaches for on-line reactor diagnostics, as well as new approaches for validating the results of computational fluidized-bed simulations with experimental measurements.

Graphical abstract

Section snippets

Introduction and background

Gas-solid fluidized-bed reactors are widely used in the chemical industry, including biomass conversion [1], [2], [3], [4], petroleum refining [5], and pharmaceutical [6], [7] and commodity chemicals production [8]. For this reason, there is widespread interest in establishing a comprehensive understanding of the gas-solid hydrodynamics to optimize processes in which fluidized-bed reactors are key components. Three of the most important hydrodynamic states or flow regimes in fluidized-bed

Fluidized bed simulation conditions

To reflect a lab-scale reactor of current relevance, we assumed the geometry of an experimental laboratory reactor used for biomass processing research at the National Renewable Energy Laboratory (NREL). A schematic of the reactor is shown in Fig. 1. The inner diameter D_r and height of the reactor H_r are 0.0508 and 1.27 m, respectively. However, for simulation purposes, the computational domain was reduced to a height of 0.4 m. Operating conditions were chosen to match baseline experiments at

Results and discussion

The visual appearance of the bubbles generated by MFiX was observed graphically in terms of void fraction iso-surfaces using Paraview [86] as illustrated in the following section below. To systematically quantify the simulated bubble patterns, we evaluated bubble statistics derived from the MFiX void fraction output using MS3DATA. We then evaluated the pressure time series features at each level to determine how they relate to the observed bubble behavior.

Conclusions

Results from the three-dimensional computational simulations of a laboratory-scale fluidized bed indicate that the transition from bubbling-to-slugging is a complex process that occurs over a range of gas flows rather than abruptly at a single flow. The transition process appears to involve a cascade of bubble coalescences that produce size and speed changes which begin near the bed surface and then progress downward toward the distributor as gas flow increases. The state of maximum slugging

Acknowledgment

This work was supported by the Bioenergy Technology Office, US Department of Energy through the Computational Pyrolysis Consortium (CPC) project. The authors would like to thank program sponsors Jeremy Leong, Cynthia Tyler, and Kevin Craig for their support and guidance. More information about the CPC project can be found at http://cpcbiomass.org/. The authors acknowledge Akhilesh Bakshi for making MS3DATA available and See Hoon Lee for discussions through email about their work related to

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^☆: Notice: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for the United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

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Computational study of the bubbling-to-slugging transition in a laboratory-scale fluidized bed☆

Highlights

Abstract

Graphical abstract

Section snippets

Introduction and background

Fluidized bed simulation conditions

Results and discussion

Conclusions

Acknowledgment

Fuel

Fuel

J. Anal. Appl. Pyrolysis

Renewable Sustainable Energy Rev.

J. Pharm. Sci.

Powder Technol.

Powder Technol.

Chem. Eng. Sci.

Int. J. Multiphase Flow

Chem. Eng. Sci.

Chem. Eng. Sci.

Chem. Eng. Res. Des.

Chem. Eng. Sci.

Powder Technol.

Powder Technol.

Int. J. Multiphase Flow

Energy

Int. J. Multiphase Flow

Powder Technol.

Energy

Chem. Eng. Sci.

Powder Technol.

Chem. Eng. Sci.

Int. J. Multiphase Flow

Powder Technol.

Chem. Eng. J. (Amsterdam, Neth.)

Chem. Eng. Sci.

Particuology

Particuology

Chem. Eng. Sci.

Powder Technol.

Powder Technol.

Powder Technol.

Chem. Eng. Sci.

Powder Technol.

Particuology

Nucl. Eng. Des.

Chem. Eng. Sci.

J. Differ. Equ.

Chem. Eng. Sci.

Chem. Eng. J. (Amsterdam, Neth.)

Chem. Eng. Sci.

Int. J. Multiphase Flow

Chem. Eng. J. Biochem. Eng. J.

Phys. A

Chem. Eng. Sci.

Flow Meas. Instrum.