(85a) Analysis of Solids Volume Fraction and Dimensionless Regime Mapping in a Circulating Fluidized Bed Riser

One of the most difficult challenges faced when trying to apply process information obtained from fluidization and hydrodynamic testing in small scale circulating fluidized beds to larger pilot or commercial scale units is identifying the correct scaleup methodology. Historically, there have been several approaches that have met with varying levels of success, including similarity methods that rely on defining and matching the values of dimensionless numbers involving different length scales.

Recent efforts by Breault et al. have focused on developing a method utilizing a dimensionless regime map incorporating use of two dimensionless ratios: U_g/U_tr2 – the ratio of the superficial gas velocity to the upper transport velocity, and Gs /Gs* - the ratio of the solids circulation rate to the saturation carrying capacity of the fluidizing gas. These recent efforts have led to the development of more accurate correlations for the Gs* as a function of riser diameter for both Geldart A- and Geldart B-type particles.

Utilizing these newly developed correlations for Gs*, fluidization data for 200-micron glass beads obtained from experiments previously conducted in the 12-inch (0.3m) diameter cold flow circulating fluidized bed (CFCFB) unit at the National Energy Technology Laboratory’s (NETL) Morgantown, WV site have been revisited considering the recently developed dimensionless regime map. The operating conditions for these experiments, when placed on the dimensionless regime map, illustrate that the tests conducted covered a range of fluidization regimes, including the dilute upflow, core annular flow, and fast fluidization regimes. This paper presents a review of the resulting dimensionless regime map via statistical and chaos analysis of riser solids fraction profiles, including recurrence analysis, to illustrate the macroscopic behavior within these different fluidization regimes.