Abstract
Results of detailed experimental measurements of solids mass flux profiles in circulating fluidized-bed risers of internal diameter 0.152 and 0.305 m are described. The ranges of superficial gas velocity and mean solids mass flux used were 3–5 m s −1 and 2–111 kg m −2 s −1, respectively, and the solids used had a surface-volume mean diameter of 74.9 μm and a particle density of 2456 kg m −3. The existence of the “similar profiles” regime first suggested by Monceaux and co-workers is confirmed. In this regime of gas—particle upflow radial profiles of reduced solids flux (local solids flux divided by cross-sectional mean solids flux) are insensitive to changes in imposed solids flux at a given superficial gas velocity. This regime is found to lie within the refluxing transport regime, characterized by a dilute, rapidly rising suspension in the core surrounded by a slowly falling denser suspension in the region adjacent to the walls. The onset of the similar-profiles regime is studied in detail and it is found that the mean solids flux, at which this regime begins, increases with superficial gas velocity. The authors' experimental findings are linked with those of other workers to produce a semi-empirical model for this regime capable of predicting profiles of solids flux and solids velocity. Comparison of predicted solids flux profiles with experimental data is very encouraging and indicates that, although the flow patterns in such vertical gas—particle systems are complex, their fluid-dynamic analysis may be relatively straightforward.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call