(78e) Maintaining Microstructure during Scaling in Circulating Fluidized Bed Risers | AIChE

(78e) Maintaining Microstructure during Scaling in Circulating Fluidized Bed Risers


Over the years there have been numerous approaches to develop scaleup methodology for circulating fluidized beds. Many of these past approaches have relied on macroscopic definitions of similitude to define dimensionless groups such as Reynolds number, Froude number, density ratios, and dimensional ratios involving different length scales. These approaches have demonstrated various levels of success, but often fail when used outside the bounds of experimental datasets. The issue with these methods is that they rely on macroscopic similitude with the hopes that those conditions would provide microscopic similitude as it does in single phase systems where the Buckingham Pi techniques have given reasonable success.

Two of the main reasons for failure are 1) changing fluidization regimes and 2) changing material properties that result in the material falling into a different Geldart group. Both are certain to change the microstructure and changes to the microstructure affect the interphase transport properties of the reactor system, namely the mass transfer and heat transfer. This work presents a new approach towards scaling based upon maintaining similitude at the microscale. It reviews a novel dimensionless flow regime map developed from analysis of the deterministic chaos parameters and higher order moments to ensure microstructure similitude. It then presents an example of using the scaling method to obtain operating conditions for a scaled-up laboratory reactor. Four scaling cases from the literature are examined to understand if the microstructure was maintained.