Risers in circulating fluidized beds

Chen, L., and Weinstein, H. The Radial Pressure Gradient in a Circulating Fluidized Bed Riser, in Circulating Fluidized Bed Technology IV (Amos A. Avidan, ed.), pp. 187-192. Somerset, Pennsylvania (1993). 

Karri, S.B.R. Knowlton, T.M. A comparison of annulus solids flow direction and radial solids mass flux profiles at low and high mass fluxes in a riser. In Circulating Fluidized Bed Technology VI Werther, J., Ed. Dechema Frankfurt, Germany, 1999 71-76. 

Optical techniques like laser doppler anemometry (LDA) can be used to obtain knowledge about the local solids hydrodynamics in CFB units close to walls at low solids fluxes [14]. Such LDA measurements of FCC particles in a riser in circulating fluidized bed have been reported by [119, 120]. 

In circulating fluidized beds two main attrition sources, namely the riser and the return leg, may be distinguished. Although a lot of information is available about solids flow patterns and flow structures inside the circulating fluidized bed risers, no systematic investigations have been found in the open literature on the influence of riser geometry and flow conditions inside the riser on attrition. With respect to attrition occurring in the return leg, the work of Zenz and Kelleher (1980) on attrition due to free fall may be mentioned (cf. Sec. 4.3). 

Grace, J. R., Influence of riser geometry on particle and fluid dynamics in circulating fluidized beds risers, in "Proceedings of the 5th International Conference of Circulating Fluidized Bed" (M. Kwauk, J. Li, Eds.), May 28-31, Beijing. 

Measurements of heat transfer in circulating fluidized beds require use of very small heat transfer probes, in order to reduce the interference to the flow field. The dimensions of the heat transfer surface may significantly affect the heat transfer coefficient at any radial position in the riser. All the treatment of circulating fluidized bed heat transfer described is based on a small dimension for the heat transfer surface. The heat transfer coefficient decreases asymptotically with an increase in the vertical dimension of the heat transfer surface [Bi et al., 1990]. It can be stated that the large dimensions of the heat transfer surface... 

Arena, U., Malandrini, A., Marzocchella, A., and Massimilla, L. Flow structures in the risers of laboratory and pilot CFB units, in Circulating Fluidized Bed Technology III (P. Basu, M. Horio and M. Hasatani, eds.), pp. 137-144. Pergamon Press, 1991. 

Rhodes, M. J., Laussmann, P., Villain, F., and Geldart, D. Measurement of radial and axial solids flux variations in the riser of a circulating fluidized bed, in Circulating Fluidized Bed Technology II (P. Basu and J. F. Large, eds.), p. 155. Pergamon Press, 1988. 

Gas Phase Hydrodynamics in Circulating Fluidized Bed Risers 261 Table 2... 

---