Lateral particle size segregation in a riser under core annular flow conditions due to the Saffman lift force

• The viscous shear Saffman force is the driving force for radial segregation.
• Small particles travel further laterally for a given time interval than larger.
• The percentage of small particles found in the core is significantly higher.

It has been observed under certain flow conditions that there is a measured increase in fine particle concentration at the center of the circulating fluidized bed riser just below the exit to the cyclone. It is hypothesized that the Saffman force might be responsible for this phenomena. Therefore, this research paper discusses the likelihood of the existence of “Saffman” forces, or lift due to viscous shear, in cylindrical, circulating fluidized bed (CFB) risers operating in the core annular regime.

Fig. 5. Caricature of particle behavior and velocity profile. [Red arrows indicate acceleration.]Figure optionsDownload as PowerPoint slide