Gas-solids contact efficiency in the entrance region of a co-current downflow fluidized bed (downer)

J. X. Zhu, Y. Ma, H. Zhang

Research output: Journal PublicationArticlepeer-review

14 Citations (Scopus)

Abstract

The contact efficiency between gas and solid phases has been investigated in the entrance region of a 9.3 m tall, 100 mm diameter gas-solids cocurrent downflow fluidized bed (downer) using FCC particles. The contact efficiency between gas and solids was estimated based on a thermal method by measuring the temperature changes of hot fluidized air in the bed. Three different distributor designs were tested under gas velocities in the range 5.2-9.3 m s-1 and solids circulation rates up to 180 kg m-2 s-1. The results show that the initial gas-solids contact efficiency is very high immediately below the distributor and that the gas and solids entrance structure (distributor design) largely influences the gas-solids contact efficiency. The results also reveal that a close relationship exists between the gas-solids mixing behaviour and the hydrodynamics in the downer. Rapid changes of the flow structure are responsible for increased gas-solids contact efficiency. The contact efficiencies also change with the operating conditions, but the effects of solids circulation rate and gas velocity seem to be different under different distributor designs.

Original languageEnglish
Pages (from-to)151-158
Number of pages8
JournalChemical Engineering Research and Design
Volume77
Issue number2
DOIs
Publication statusPublished - Mar 1999
Externally publishedYes

Keywords

  • Contact efficiency
  • Downer
  • Entrance region
  • Hydrodynamics
  • Mixing

ASJC Scopus subject areas

  • Chemistry (all)
  • Chemical Engineering (all)

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