Influence of the nature of the Roots blower on pressure fluctuations in a fluidized bed

Experiments were conducted in a 0.29-m I.D. fluidized-bed cold model with fluidizing air supplied by a Roots blower. To investigate the influence of the air-supply equipment on the pressure fluctuations, another experiment was carried out in a 0.10-m I.D. cold model with fluidizing air supplied by a compressor. In this work, the effects of superficial air velocity, static bed height and windbox volume were studied. The pressure pulsation frequency caused by the Roots blower was identified successfully from the pressure fluctuation frequency spectrum. This pulsation frequency was found to be related to the blower impeller rotary speed and exhibited a good linear relationship. The experimental results indicated that the blower possesses its own pressure pulsation frequency vs. superficial air velocity characteristic curve. At a given air flow rate, a larger-scale blower produced a lower pulsation frequency, higher pulsation intensity and a higher coefficient of variation for pressure fluctuations in the bed. With increasing superficial air velocity, the pulsation intensity abated and became less influential on the pressure fluctuations in the bed.