EFFECTS OF DIFFERENT PARAMETERS ON THE ON SET OF FLUIDIZATION IN A TURBULENT REGIME

Much controversy exists in the literature about the effects of differe nt variables on the onset of the turbulent regime in gas-solid fluidiz ation, U-c, and on the transport velocity, U-tr. In order to study the effect of four hydrodynamic factors upon these transition velocities, a basic 8-run Plackett-Burman design was used. The factors and their level were: (a) diameter of column (82 vs 200 mm), (b) particles (FCC vs Sand), (d) static bed height (300 vs 450 mm) and (g) size distribut ion of particles (narrow vs wide). In each run, U-c and U-tr were dete rmined experimentally by means of differential pressure transducer and also with a capacitance probe. The experimental results and statistic al analysis show that bed diameter has the most important impact (61% variability upon U-c and 51% upon U-tr). The product of particle size and density (p(p)d(p)) seems to have a significant effect (35% variabi lity upon U-c and 47% upon U-tr). Static bed height has a slight impac t. There is essentially no effect of the particle size distribution. R esults show that interactions effects are negligible between these fac tors. Finally, two correlations for U-c and U-tr, which are in agreeme nt with literature data are proposed.