Gas-solids flow behavior: CFB Riser vs. Downer

Citation
H. Zhang et al., Gas-solids flow behavior: CFB Riser vs. Downer, AICHE J, 47(9), 2001, pp. 2000-2011
Citations number
41
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Chemical Engineering
Journal title
AICHE JOURNAL
ISSN journal
0001-1541 → ACNP
Volume
47
Issue
9
Year of publication
2001
Pages
2000 - 2011
Database
ISI
SICI code
0001-1541(200109)47:9<2000:GFBCRV>2.0.ZU;2-X
Abstract
Comparisons are made in a circulating fluidized-bed riser/downer system bet ween a 15.1 in high, 0.10 m ID riser and a 9.3 in high, 0.10 in ID downer, based oil the measurements of the radial distributions of the local solids holdups and local particle velocities along the two columns. Although the c ore-annulus flow structures exist in both the riser and downer, the radial flow structure in the downer differs largely from that in the riser. The ra dial distributions of solids holdup and particle velocity ill the downer ar e much more uniform than those in the riser, thus ensuring the low back mix ing and the nan-ow particle residence time distribution in the downer. The axial flow structure in the downer is also more uniform than that in the ri ser. Due to the high particle acceleration and the high particle velocity, in the downer, the overall solids holdup is significantly, lower than that in the riser. The microflow structure in the downer, characterized by, the low intermittency, indices, is also more uniform than that in the riser. Th ese key properties of the downer make it a very promising candidate for ind ustrial applications where short reaction times and high product selectivit y, are required.