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 language | English |
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Pages (from-to) | 151-158 |
Number of pages | 8 |
Journal | Chemical Engineering Research and Design |
Volume | 77 |
Issue number | 2 |
DOIs | |
Publication status | Published - Mar 1999 |
Externally published | Yes |
Keywords
- Contact efficiency
- Downer
- Entrance region
- Hydrodynamics
- Mixing
ASJC Scopus subject areas
- General Chemistry
- General Chemical Engineering