Acoustic signals emitted from particles and bubbles in the gas-solid fluidized bed were collected by the transducer located under the distributor and the result showed that the energy and deviation of acoustic signals varied regularly with superficial velocity.Superficial velocity was the minimum fluidizing velocity or the minimum turbulent velocity

while energy or deviation changed suddenly.Then a criterion to determine the change of flow pattern was obtained that when the ratio of acoustic energy or deviation reached the maximum

the velocity was the minimum fluidizing velocity

while the ratio of acoustic energy or deviation reached the next maximum the corresponding velocity was the minimum turbulent velocity.Experiments were carried out in a fluidized bed with inner diameter of 250 mm and polyethylene resin particles.The minimum fluidizing and minimum turbulent velocity obtained from the new method agreed well with those deducted from classical equations and traditional methods

including pressure difference method and pressure fluctuation method.In conclusion

an easy

sensitive

exact and on-line way to detect fluidizing velocity is presented

and this method is applicable to industrial equipment.