A comparison of flow development in high density gas-solids circulating fluidized bed downer and riser reactors

Comparison of flow development in high density downer and riser reactors is experimentally investigated using fluid catalytic cracking particles with very high solids circulation rate up to 700 kg/m2s for the first time. Results show that both axial and radial flow structures are more uniform in dow...

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Bibliographic Details
Published in:AIChE journal 2015-04, Vol.61 (4), p.1172-1183
Main Authors: Wang, Chengxiu, Li, Chunyi, Zhu, Jesse, Barghi, Shahzad
Format: Article
Language:English
Subjects:
Agglomeration
Catalytic cracking
Chemical engineers
Chemical reactions
Chemical reactors
Circulating
Comparative analysis
Contact
downer
flow development
Fluidized beds
High density
particle velocity
Reactors
riser
Risers
Slip velocity
solids holdup
Velocity
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Summary:Comparison of flow development in high density downer and riser reactors is experimentally investigated using fluid catalytic cracking particles with very high solids circulation rate up to 700 kg/m2s for the first time. Results show that both axial and radial flow structures are more uniform in downers compared to riser reactors even at very high density conditions, although the solids distribution becomes less uniform in the high density downer. Solids acceleration is much faster in the downer compared to the riser reactor indicating a shorter length of flow development and residence time, which is beneficial to the chemical reactions requiring short contact time and high product selectivity. Slip velocity in risers and downers is also first compared at high density conditions. The slip velocity in the downer is much smaller than in the riser for the same solids holdup indicating less particle aggregation and better gas‐solids contacting in the downer reactors. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1172–1183, 2015
ISSN:0001-1541
1547-5905
DOI:10.1002/aic.14728