Prediction of the minimum fluidization velocity for fine particles of various degrees of cohesiveness

Based on the well-known Ergun equation and the force balance of a particle bed under fluidization bringing into account the interparticle forces, a new correlation for prediction of the minimum fluidization velocity (u_mf) for fine particles of various degrees of cohesiveness has been derived. For the first time, a general correlation of the minimum fluidization voidage (ε_mf) versus particle size is obtained from various sets of experimental data. The newly derived umf correlation combined with the one for ε_mf proves to be superior to the traditional ones proposed by Leva (1959) and Wen and Yu (1966), especially for the cases where very fine or very large particles are employed in fluidization. The correlations of Leva (1959) and Wen and Yu (1966), both disregarding the cohesive-force effect and the effect of particle size on ε_mf, result in noticeable errors in u_mf prediction for very fine (Geldart groups C and C/A) and very large (Geldart group D) particles, although they work satisfactorily for small-to-medium size particles (Geldart groups B and A). In contrast, the prediction with the new correlation shows good agreement with the experimental data for various types of particles ranging from Geldart group C to group D.