Linear stability analysis of gas-fluidized beds for the prediction of incipient bubbling conditions

This work focuses on the development of a novel linear stability criterion for the state of homogeneousfluidization regime, based on a new mathematical model for gas-fluidized beds. The model is developedstarting from the well-known particle bed model. A mono-dimensional momentum balance is derivedleading to a set of equations which explicitly include voidage-gradient dependent terms (elastic force)for both solid and fluid phases.A fully predictive criterion for the stability of homogeneous fluidization state is here proposed, basedon the well-known Wallis’ linear stability analysis. The criterion requires the choice of an appropriateaveraging distance, which in the present development is found to be bed-voidage dependent. The linearstability criterion resulted in turn in a simple, yet fully predictive, relationship for incipient bubblingvoidage.Validation was carried out analyzing the influence of all physical properties and sensitivity to closurerelations, showing substantial agreement with literature data.