On the Two-Phase Theory of Group C+ and Geldart Group A Particles

The relative distribution of gas flow between the bubble phase and dense phase is a very important factor that determines the performance of a gas-solid fluidized bed reactor because the dense phase provides a better gas-solid contact than the bubble phase. The gas flow through the dense phase was initially considered to be at minimum fluidization (the so-called two-phase theory) but was found to be higher with fine Group A particles. Using even smaller particles in this study, the fluidization of Group C+ particles, Geldart Group C particles with nano-additives, exhibited lower bubble rise velocity, lower bubble holdup, and higher gas holdup in the dense phase, etc., signifying more gas flow through the dense phase and subsequently contributing to better gas-solid contact than other particles that have ever been tested, being Group A or B. The correction factor Y that accounts for increased dense-phase gas flow in the modified two-phase theory was also found to be not a constant but a function of the superficial gas velocity, and a correlation was then proposed to characterize the division of gas flow between the two phases for these fine Group C+ particles based on the experimental results. The higher dense-phase gas velocity and lower bubble-phase gas velocity could improve the gas-solid contact and reactor performance for Group C+ particles.