CHARACTERIZATION OF THE FLOW TRANSITION BETWEEN BUBBLING AND TURBULENT FLUIDIZATION

A lot of controversy exists in the literature on the actual boundaries of the turbulent regime in gas-solid fluidization. This work shows th at this disagreement results from the type of experimental techniques used. It is found that the onset of turbulent fluidization is at U(c) and that the velocity U(k), which has often been reported in the liter ature, is an artifact due to the use of differential pressure transduc ers. Experiments conducted for sand and fluid cracking catalyst (FCC) particles with differential and absolute pressure transducers and with a capacitance probe show that U(c) is the velocity at which bubbles a nd slugs reach their maximum size. At gas superficial velocities highe r than U(c), the breakup of bubbles increases while the formation and coalescence of these bubbles decrease. The turbulent regime ends at th e transport velocity.