Wavelets analysis of pressure fluctuation in agitated fluidized bed
In an agitated fluidized bed using Geldart D particles as fluidized materials with a static bed height of 400 mm and an inner diameter of 188 mm, the pressure fluctuation signals at different rotation speeds of stirrer blade and gas velocities were analyzed with the wavelet analysis method for investigating the influence of agitation of stirrer blade on the fluidization behavior.The pressure fluctuation signals were decomposed into 9 scales by Dau2 wavelet.Experimental results indicated that the wavelet energy characteristics of Scale 1 detailed signal changed sharply in a certain range of gas velocity.Then the criteria of the minimum bubbling velocity and full bubbling velocity were developed.The Geldart D particles showed particulate fluidization due to the rotation of stirrer blade.The minimum bubbling velocity and full bubbling velocity increased linearly with increasing rotation speeds of stirrer blade, while the fluidized bed transformed from bubbling fluidization to particulate fluidization.Gas velocity was the major cause for the pressure fluctuation in the bubbling fluidization regime and increasing rotation speed of stirrer blade had little effect on the bubble frequency, but made the bubble size smaller obviously.