(74b) Distinctions between Circulating-Turbulent Fluidized Beds, Turbulent Fluidized Beds and High-Density Circulating Fluidized Beds

Transient flow behaviors in a novel circulating-turbulent fluidized bed (C-TFB) were investigated by a novel multi-functional optical fiber probe, being capable of measuring simultaneously local instantaneous solids volume concentration, velocity and flux in gas-solid two-phase suspensions. Micro hydrodynamic distinctions between the gas-solid suspensions in a turbulent fluidized bed (TFB), conventional circulating fluidized bed (CFB), high-density circulating fluidized bed (HDCFB) and the newly designed C-TFB were also intensively studied. The experimental results show that particle-particle interactions (collisions) dominate the motion of particles in the C-TFB and TFB, totally different from the interaction mechanism between the gas and solids phase in the conventional CFB and the HDCFB, in which the movements of particles are mainly controlled by the gas-particle interactions (drag forces). Turbulence intensity and frequency in the C-TFB are greater than those in the TFB at the same superficial gas velocity. As a result, the circulating-turbulent fluidization is a new flow regime, independent of turbulent fluidization, fast fluidization and dense suspension upflow. The gas-solid flow in the C-TFB has its inherent hydrodynamic characteristics, different from those in TFB, CFB and HDCFB reactors.