EFFECT OF PARTICLE-SIZE DISTRIBUTION IN DIFFERENT FLUIDIZATION REGIMES

The effect of particle size distribution (PSD) on the performance of a fluidized-bed reactor was investigated in different hydrodynamic regimes: bubbling, slugging, turbulent and fast fluidization, with three particle size distributions, all with the same mean diameter and nearly the same particle density and BET surface area. Regime transitions were examined by measuring pressure fluctuations. Void sizes tended to be smaller and the transition from bubbling or slugging to turbulent fluidization was achieved earlier for the wide distribution powder than for the narrow PSD. At gas velocities less-than-or-equal-to 0.2 mls, the conversion and reactor efficiency were not affected greatly by the PSD. However, at higher gas velocities, PSD played a significant role. For particles of wide size distribution, the conversion in the turbulent and fast fluidization regimes was usually higher than in the bubbling fluidization regime at the same dimensionless rate constant, k(f)'. On the other hand, for particles of narrow size distribution, the dependence of conversion on the regime is small, except for the fast fluidization regime.