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<p>Unlike the usual designs of fluidized beds, a challenging design of a narrow-tubes fluidized bed equipped with a two heat exchangers riser assembly, is proposed to provide the largest heat transfer areas per unit length ever used for highly exothermic catalytic reactions such as polymerization reactions, synthesis of polypropylene and oxidative coupling of methane, OCM. The riser consists of a bottom double-pipe and an upper shell and tube heat exchangers of a tube bundle consisting of 69 tubes, each of 6.0&#xa0;mm I.D. This design provides sufficiently large heat transfer area suitable for highly ectothermic and/or endothermic catalytic reactions. Cold-model experiments were carried out to examine gas–solid flow and heat transfer phenomena in terms of elutriation rates, pressure distributions and convective heat transfer coefficients. Experiments used two different sizes of Geldart-A charcoal particles (150~250&#xa0;μm and 90~150&#xa0;μm) and Geldart-B sand particles (150~250&#xa0;μm). Elutriation rates for the Geldart-A and Geldart-B particles increased with increasing gas velocities and increased with increasing particles` loadings. Larger rates were noticed for smaller size Geldart-A particles compared to the denser Geldart-B particles. Fluidization runs smoothly with high reproducibility for charcoal particles up to 3.0&#xa0;kg. Empirical correlations for the convective heat transfer coefficients for non-spherical charcoal particles with air were developed with reasonable accuracy using a bi-section model and particles` rising velocities at air velocities larger than the particle falling velocities.</p>

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Gas–Solid Flow and Heat Transfer Phenomena in a Novel Design of a Narrow-Tubes Fluidized Bed (NTFB)

  • 期刊论文

  • 发表日期：

    2026年4月8日

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  • Emad A. M. Abdelghani

摘要

Unlike the usual designs of fluidized beds, a challenging design of a narrow-tubes fluidized bed equipped with a two heat exchangers riser assembly, is proposed to provide the largest heat transfer areas per unit length ever used for highly exothermic catalytic reactions such as polymerization reactions, synthesis of polypropylene and oxidative coupling of methane, OCM. The riser consists of a bottom double-pipe and an upper shell and tube heat exchangers of a tube bundle consisting of 69 tubes, each of 6.0 mm I.D. This design provides sufficiently large heat transfer area suitable for highly ectothermic and/or endothermic catalytic reactions. Cold-model experiments were carried out to examine gas–solid flow and heat transfer phenomena in terms of elutriation rates, pressure distributions and convective heat transfer coefficients. Experiments used two different sizes of Geldart-A charcoal particles (150~250 μm and 90~150 μm) and Geldart-B sand particles (150~250 μm). Elutriation rates for the Geldart-A and Geldart-B particles increased with increasing gas velocities and increased with increasing particles` loadings. Larger rates were noticed for smaller size Geldart-A particles compared to the denser Geldart-B particles. Fluidization runs smoothly with high reproducibility for charcoal particles up to 3.0 kg. Empirical correlations for the convective heat transfer coefficients for non-spherical charcoal particles with air were developed with reasonable accuracy using a bi-section model and particles` rising velocities at air velocities larger than the particle falling velocities.