Mechanism of Fast Fluidization and Vertical Profile of Solid Concentration in Fast Fluidized Beds

The gas velocity in the circulating fluidized beds of, for example, aluminum ore calciners, petroleum crackers and boilers is larger than the particles' terminal velocity. We propose the growing chain model, in which the particles form vertical chains in the fluidized bed, in order to determine theoretically the regimes of fast fluidization. Comparing the fluidization condition empirically recognized as the optimum operating condition for the circulating fluidized bed in boilers, the maximum fast fluidization gas velocity is found to coincide with the terminal velocity of an infinitely long chain, which is about twice as high as that of a single particle.