Solids lateral mixing and compartmentalization in dynamically structured gas–solid fluidized beds

Laurien A. Vanderwalle, Victor Francia, Kevin M. van Geem, Guy B. Marin, Marc-Olivier Coppens

Research output: Contribution to journalArticlepeer-review

1 Citation (SciVal)

Abstract

An adequate use of gas pulsation can create an ordered, dynamically structured bubble flow in a bed of Geldart B particles. A structured bed is more homogeneous, responds to external control and is scalable. While earlier studies have focused on describing the self-organization of the gas bubbles, the solid mixing and gas–solid contact patterns have remained unclear. In this work, the solids circulation and mixing behavior in structured and unstructured beds at various pulsation frequencies are compared with a traditional fluidized bed operation. The degree of lateral mixing is hereby quantified through an effective lateral dispersion coefficient extracted from CFD-DEM (discrete element modelling) simulations in a thin fluidized bed system. Mixing shows major quantitative and qualitative differences amongst the investigated cases. The coordinated motion of the gas bubbles wraps the solid flow into a series of compartments with minimal interaction, whereby effective lateral dispersion coefficients are an order of magnitude lower than in an unstructured operation. More importantly, unlike a traditional bed, dispersion in a structured bed is driven by advection and is no longer a diffusive process. Compartmentalization decouples the time scales of micro- and macromixing. Every pulse, the compartments rearrange dynamically, causing a level of local axial mixing that is scale-independent. While further work is necessary to fully understand the compartmentalization at a larger scale, the circulation described here indicates that a dynamically structured bed can provide a tight control of mixing at low gas velocities and a narrower distribution of stresses in the solid phase compared to traditional devices.

Original languageEnglish
Article number133063
JournalChemical Engineering Journal
Volume430
Issue numberPart 4
Early online date21 Oct 2021
DOIs
Publication statusPublished - 15 Feb 2022

Keywords

  • CFD-DEM
  • Lateral dispersion
  • Mixing
  • Pulsation
  • Structured fluidized bed

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry
  • Chemical Engineering(all)
  • Industrial and Manufacturing Engineering

Fingerprint

Dive into the research topics of 'Solids lateral mixing and compartmentalization in dynamically structured gas–solid fluidized beds'. Together they form a unique fingerprint.

Cite this